Concepts and applications of electronic guns through the anodes and cathodes to the capacitor plate until perfect to the target with the learning process of training : comparing anodes and cathodes and capacitors <---> theory and application of electron shots on the Target <---> stabilize the shot of electrons on the target AMNIMARJESLOW GOVERNMENT 91220017 XI XA PIN PING HUNG CHOP 02096010014 LJBUSAF GO FAR ELECTRON GUN JUMPING TO TARGET UNTIL REGARDLESS THE ENDING STABILIZATION ELECTRONIC TARGET PRO SPACE LIFE 2020 ^_^ GUN STREAM ROLL OVER ROBOTICS 2*2 0717 E-EYESRAM

                                 


                                        Electron gun; potentials around charged plates      

An electron gun releases electrons by thermionic emission and accelerate the electron through charged plates, and that the electrons are not gaining any energy after they leave the gap between the plates. I'm confused about charges/potentials around the charged plates.
  
An infinitely long and wide plate will, indeed, produce a constant potential. The electrostatic force acting on a charge in a constant potential is zero, so in the ideal case the charges won't move. The solution to your paradox is that plates of infinite extensions don't exist.
What we mean by "infinite size plates" are plates that are so large that the potential sufficiently close to them is sufficiently constant. It can never be exactly constant, except on a conducting surface.
In the region between two parallel plates of different charge that are close enough together the potential is a linear function and the force is constant. This is a plate capacitor that can also be used to accelerate charges. Outside of the plates there is a substantial fringe field with a complicated field that extends all the way to infinity. 

The beam of electrons as a result of thermionic emission.
In an electron gun, the emitted electrons from the cathode become incident at a point on the other end of the tube, as they travel through a gap allocated in the anode.   the motion of the electrons from the cathode to the anode is as a result of the electric field, and as a result, the electrons are accelerated towards the positively charged anode. 

1. the cool thing about the parallel plate arrangement of electrodes in an electron gun. The field is strong and (fairly) uniform in the the space between the plates but much less outside of the plates. In the ideal case of a pair of infinitely large plates with an equal and opposite uniform charge distribution, the field outside the plates would be zero. If you have a point charge the electric field strength decreases proportionally to the distance from it squared. If you have an infinitely long line of charge the electric field strength decreases proportionally to the distance (not distance squared). But, if you have an infinite plane of charge the electric field strength it produces is the same - independent of the distance to the plane. Now, say you put your positive plate on the bottom it will produce an electric field directed upwards above it (away from the positive plate). If you then put a negatively charged plate above the positive plate it will produce an upward field below it (towards the negative plate). These two fields are both in the same direction and so result in a strong field. But, the negative plates field above itself is downwards (still towards it) and the field there from the positive plate is upwards (still away from it). So in the region above the negative plate (or below the positive plate) the fields from each are in opposite directions and, since the distance from the plates does not affect their strength, they cancel out completely. Obviously in an electron gun the anode and cathode are not infinitely large but even with finite plates the field "outside" of the anode is much, much smaller than on the field between the plates so the electron is not pulled back. Having written all this and then looked at some images of electron guns I realize the the version I described is a simplified one with a hot filament between two planar electrodes. The geometry of practical electron guns is a bit different.
2. Thermionic emission gets the electrons out of the metal filament but I don't think you can really call the electrons a cathode ray until you accelerate them. A regular incandescent light bulb will produce thermionic emission but the emitted electrons are just attracted back to filament. There are cold cathode devices that emit electrons by means other than thermionic emission.

                            XXX  .  XXX The example Theory of electron Gun on Tele Vision 

A series of cathode ray tubes graphically demonstrate various properties of the electron. Cathode Ray Tube provides evidence that cathode rays are not visible to human eyes. Cathode Ray Tube  cathode rays cast a shadow behind a Maltese Cross. Cathode Ray Tube  light shined on a pinwheel inside a CRT does not cause the pinwheel to move.  However, when cathode rays strike the pinwheel inside the CRT, the pinwheel begins to spin and move.  Cathode Ray Tube  in a darkened room, the electron beam (cathode rays) shows up on a phosphor screen as a bright blue line.  The electron beam is deflected by an electric field and a magnetic field.

Electrons travel in straight lines from the cathode towards the anode (Maltese Cross CRT).  Cathode Rays are particles and have mass because cathode rays cause a metal pinwheel inside a CRT to turn.  Cathode rays have a negative charge because J.J. Thompson's experiment showed the cathode rays being pulled toward the positive capacitor plate and away from the negative charge plate and a magnetic field deflects the cathode rays in a direction consistent with the rays being negatively charged particles.

The electrons are emitted by a heated filament and are accelerated by a positively charged screen in the electron gun. When the electrons strike the phosphorescent screen they excite the electrons of the phosphorescent material into higher energy states. As the electrons move back down into ground state they emit visible light.

Deflection of Cathode Rays by an Electric Field - The application of high voltage to capacitor plates creates an electric field.  When a cathode ray is passed through this electric field, the negatively charged electrons are deflected toward the positive charged plate and away from the negatively charged plate.  Like charges repel, unlike charges attract.

Deflection of Cathode Rays by a Magnetic Field- The magnet creates a magnetic field perpendicular to the electron beam and parallel to the plane of the tabletop. The magnetic field deflects the electrons according to the right hand rule.

Materials 

• cathode ray tube
• high voltage DC/ 120 VAC power supply for electron gun and heater coil
• high voltage DC power supply for deflection plates
• power strips
• jumper cables with banana plugs to connect everything
• a fairly powerful magnet

Procedure 

Deflection of Cathode Rays (electron beam) by an Electric Field - Turn on the power strip. Turn on the power to both high voltage sources. Dim the houselights. Turn up the power on the high voltage source connected to the electron gun. The trace of a cathode ray should appear on the phosphorescent screen. Turn up the power on the high voltage source connected to the capacitor plates. The cathode ray should be deflected upward. Turn down both power supplies all the way. If desired, switch the leads going to the deflection plates and repeat the process. The cathode ray should be deflected downward.

Deflection of Cathode Rays by a Magnetic Field - Turn on the power strip. Turn on the power to both high voltage sources. Dim the houselights. Turn up the power on the high voltage source connected to the electron gun. The trace of a cathode ray should appear on the phosphorescent screen. Bring one end of the magnet close to the front of the tube perpendicular to the axis of the beam. The cathode ray should be deflected either upward or downward depending on which pole of the magnet is close to the beam. Turning the magnet around so that the other pole is closest to the magnetic field should cause deflection of the cathode rays in the opposite direction. Turn down both power supplies all the way. 

Movement of a Pinwheel in a CRT by Interaction with Cathode Rays - cathode rays striking a pinwheel inside a CRT move the pinwheel. 

Cathode Rays striking a Maltese Cross inside a CRT, produces a shadow.  Provides evidence that the cathode rays originates at the cathode and travels toward the anode.

 

Safety Precautions 

Be careful not to touch any of the high voltage leads while the power is on. The glass tube is fragile and evacuated. Wear eye protection in case of implosion.

Prep. Notes 

Cathode Ray Tube

• All materials are obtained from the physics demo prep room.
• Connect the high voltage output from the high voltage DC/ 120 VAC power supply to the electron gun of the cathode ray tube (CRT). The negative lead goes in the jack in the center of the back of the electron gun part of the CRT. The positive lead goes in the jack on the side of the electron gun part of the CRT.
• Connect the leads from the 120 VAC output of the high voltage DC/ 120 VAC power supply to the CRT. One lead piggybacks onto the back of the high voltage negative lead and the other goes into the other jack right beside it, off-center on the back of the electron gun part of the CRT.
• Connect the leads from the other high voltage DC power source to the deflector plates at the top and bottom of the CRT. The positive lead should be connected to the top and the negative lead should be connected to the bottom.
• Plug both of the power supplies into the power strip and plug the power strip into an outlet.

 
                           XXX  .  XXX 4%zero Difference Between Anode and Cathode

 Anode vs Cathode

                             

Anode and cathode are two terms that are often used interchangeably with positive and negative in batteries. Most of the time there is no problem with it as the definition would often match the practice. However, there are certain scenarios where this is not true.

The anode, by definition, is the electrode where electricity flows into. In contrast, the cathode is the electrode where the electricity flows out of. If we look at a battery connected to a load, like a bulb for example, the electricity flows from the positive terminal to the negtive terminal. In this case, the positive terminal is the cathode, and the negative terminal is the anode. But when the battery is being charged, the electricity flows into the positive terminal instead of out of it. In this case, the roles are reversed, and the positive terminal becomes the anode and the negative terminal is the cathode.

The reversal is also very noticeable when you are dealing with components like diodes and capacitors since these components absorb electricity unlike batteries. The anode of capacitors and diodes is the side that you connect to the positive terminal since that’s where the electricity enters, and the negative terminal is the cathode because that is where the electricity leaves.

Because of the confusion with regards to the current flow and where the anode and cathode is, it is probably better to use the terms positive and negative terminals instead. It is constant and doesn’t change regardless of the current flow.

Aside from being used together, there are also applications where they are not together. A good example of this is the sacrificial anode coating, usually zinc, used to protect metals. This is common in ships where the flow of water creates a static charge. The sacrificial anode absorbs this charge and slowly disintegrates. In this manner, the underlying metal doesn’t get damaged, and only the coating needs to be restored every so often.

Summary:
1. The cathode is typically the negative  side while the anode is the positive side.
2. The anode is the electrode where the electricity flows into it.
3. The cathode is the electrode where the electricity flows out of it.

Difference between Capacitor and Battery

What is a Battery?

A battery is an electronic device made of one or more cells which converts the chemical energy packed within its active materials into electrical energy to provide a static electrical charge for power.
Electrons are produced through electrochemical reactions which involves transfer of electrons via an electronic circuit.
In simple terms, battery is a constant source of power which supplies electricity in the form of direct current (DC). A battery usually contains a positive (+ve) and a negative (-ve) terminal.
The cell is the basic power unit of the battery which consists of three main bits. Plus there are two electrodes and a chemical called an electrolyte which fills the gap between the electrodes.

When the electrodes are connected to a circuit, the electrons cross from the negative to the positive terminal, eventually creating an electrical charge. Energy is stored inside the battery in the form of chemical energy which gets converted into electrical energy, releasing electricity through a chemical reaction which eventually generates an electric current.



Take an example of a flashlight. When you put alkaline batteries into the flashlight and turn the switch on, you do nothing but complete the circuit. The chemical energy stored within the battery gets converted into electrical energy, which then travels out of the battery, causing the flashlight to light up. This is because the electrons are crossing through the circuit.
The cathode and anode are generally made of different materials. The positive electrode contains a material that gives up electrons quite easily such as lithium.
The electrons get to the cathode only through a circuit which is external to the battery. The electrolyte – the most crucial part in the operation of a battery – transports ions between the chemical reactions that occur in the electrodes.
These chemical reactions are collectively called as oxidation-reduction reactions.

What is a Capacitor?

A capacitor (also known as a condenser) is also an electronic component that stores electrostatic energy in an electric field.
They are more like a battery but they are used for entirely different purpose. While a battery uses chemical reactions to store electrical energy and releases power very slowly through an electronic circuit, capacitors are capable of releasing energy very rapidly.
A capacitor contains at least two electrical conductors separated by an insulator (dielectric). When an electric field develops across the insulator, it stops the flow and an electric charge is starting to build up on the plates.

can find all types of capacitors ranging from small capacitor beads found in resonance circuits to high power correction capacitors used for large scale operations.
A capacitor basically consists of two or more metal plates which are not connected to each other but are electrically separated by a non-conducting substance such as ceramic, porcelain, cellulose, mica, Teflon, etc.
The dielectric generally dictates what type of capacitor it is and for what it can be used ideally. While some capacitors are ideal for high frequency operations, while some are best suited for high voltage applications.

Difference between Capacitor and Battery

1. Definition of Capacitor and Battery  – While a battery stores its potential energy in the form of chemical reactions before converting it into electrical energy, capacitors store potential energy in an electric field. Unlike a battery, a capacitor voltage is variable and is proportional to the amount of electrical charge stored on the plates.
2. Application of Capacitor and Battery – A battery can usually store a larger amount of electrical charge, while a capacitor, on the other hand, are capable of handling high voltage applications and ideal for high frequency uses.
3. Charge/Discharge Rate  of Capacitor and Battery – The rate at which a capacitor is able to charge and discharge is usually faster than what a battery is capable of because a capacitor stores the electrical energy directly onto the plates. The process gets delayed a bit in case of a battery due to the chemical reaction involved while converting chemical energy into electrical energy.
4. Energy Storage  of Capacitor and Battery – While both electronic devices are used to store electrical energy, the way they do vary dramatically. A battery stores electrical energy in the form of chemical energy, while a capacitor stores electrical energy in a magnetic field. This is why batteries store a lot of charge but they charge/discharge very slowly.
5. Polarity of Capacitor and Battery – The polarity of the electronic circuit must be reverse while charging a battery, while it must be same as it is supposed to be while using in case of a capacitor. A battery maintains a constant voltage flow across the terminals and it is discharged only when the voltage goes down.

Capacitor vs. Battery : Comparison Table

Battery	Capacitor
A battery stores its potential energy in the form of chemical energy.	A capacitor uses electrostatic field to store electrical energy.
It has a better energy density which means more energy per volume can be stored.	It has a comparatively low energy density than a battery.
It is basically a DC component.	It is ideally used for AC applications.
Charge/discharge rate is relatively slower than capacitors.	Charge/discharge rate is usually faster than a battery because it stores energy directly onto the plates.
Charges are not separated in a battery.	Electrons are pre-stocked in capacitors.
Battery runs for a longer time.	Capacitors discharge almost instantaneously.

Summary points on  Capacitor and Battery

Both batteries and capacitors are electronic devices capable of storing electrical charge and they seem awfully similar as they both release electrical energy. However, the way they do it vary dramatically. While a battery stores potential energy in the chemical form, a capacitor stores its potential energy in an electrostatic field. In simple terms, batteries store and distribute energy in a linear form – like a constant electrical flow. Capacitors, on the other hand, distribute energy in short bursts. A capacitor stores energy directly onto the plates which makes charging/discharging a bit faster than batteries. However, batteries are capable of regaining their stored energy much efficiently and for a longer duration than capacitors.

                                                   ADP Motor Run Capacitors


 


ADP (Metalized Polypropylene) motor run capacitors are compact, self-healing products that find greatest utilization as motor-run capacitors in fractional horsepower electric motors. However, the motor run capacitors may be used in a wide variety of 50/60 Hz. AC or DC applications.
The motor run capacitors are available in capacitances up to 30 microfarads and with voltage ratings of 250, 370, and 440 VAC. The metalized polypropylene film dielectric provides excellent electrical characteristics including stable capacitance over time and temperature and a very low Dissipation Factor (internal heating).
The motor run capacitors’ integral mounting ear makes it an excellent choice for difficult to mount applications and the choice of terminal configurations is another big plus. Terminal configuration includes single or double 0.187 or 0.250 spade terminals fast-on, insulated wire leads, or PC-mount pins. ADP motor run capacitors can be supplied with a “lay-down” type bracket which provides additional mounting options. Other options available include P2 protected segmented film (ADP series).
ADP motor run capacitors offer UL, cUL, VDE, TUV, and CE approvals available. All ADP motor run capacitors are also RoHS compliant.

Technical Specifications
Capacitance	0.12 ~ 30 uF (±5%)
Rated Voltage	250 ~ 440 VAC
Frequency	50/60 Hz
Dissipation Factor	≤ 0.002 (100 Hz)
Operating Temperature	-25 ~ +85 °C
Dielectric Material	Metalized Polypropylene
Case Material	Flame Retardant Plastic (UL94 V-0)

Terminal Configurations
(t)	TERMINAL STYLE	IMAGE
A	Single AMP.187 Fast-On
C	Double AMP.187 Fast-On
E	Single AMP.250 Fast-On
F	Double AMP.250 Fast-On
M	Insulated Wire Leads
S	PC-mount Pins

                               XXX  .  XXX 4%zero null 0 Linear particle accelerator

A linear particle accelerator (often shortened to linac) is a type of particle accelerator that accelerates charged subatomic particles or ions to a high speed by subjecting them to a series of oscillating electric potentials along a linear beamline. The principles for such machines were proposed by Gustav Ising in 1924, while the first machine that worked was constructed by Rolf Widerøe in 1928  at the RWTH Aachen University. Linacs have many applications: they generate X-rays and high energy electrons for medicinal purposes in radiation therapy, serve as particle injectors for higher-energy accelerators, and are used directly to achieve the highest kinetic energy for light particles (electrons and positrons) for particle physics.
The design of a linac depends on the type of particle that is being accelerated: electrons, protons or ions. Linacs range in size from a cathode ray tube (which is a type of linac) to the 3.2-kilometre-long (2.0 mi) linac at the SLAC National Accelerator Laboratory in Menlo Park, California.

                                                     

The linier Particle within the Australian Synchrotron uses radio waves from a series of RF cavities at the start of the linac to accelerate the electron beam in bunches to energies of 100 MeV.

Construction and operation

Schema of a linear accelerator

A linear particle accelerator consists of the following elements:

• The particle source. The design of the source depends on the particle that is being moved. Electrons are generated by a cold cathode, a hot cathode, a photocathode, or radio frequency (RF) ion sources. Protons are generated in an ion source, which can have many different designs. If heavier particles are to be accelerated, (e.g., uranium ions), a specialized ion source is needed.
• A high voltage source for the initial injection of particles.
• A hollow pipe vacuum chamber. The length will vary with the application. If the device is used for the production of X-rays for inspection or therapy the pipe may be only 0.5 to 1.5 meters long. If the device is to be an injector for a synchrotron it may be about ten meters long. If the device is used as the primary accelerator for nuclear particle investigations, it may be several thousand meters long.
• Within the chamber, electrically isolated cylindrical electrodes are placed, whose length varies with the distance along the pipe. The length of each electrode is determined by the frequency and power of the driving power source and the nature of the particle to be accelerated, with shorter segments near the source and longer segments near the target. The mass of the particle has a large effect on the length of the cylindrical electrodes; for example an electron is considerably lighter than a proton and so will generally require a much smaller section of cylindrical electrodes as it accelerates very quickly. Likewise, because its mass is so small, electrons have much less kinetic energy than protons at the same speed. Because of the possibility of electron emissions from highly charged surfaces, the voltages used in the accelerator have an upper limit, so this can't be as simple as just increasing voltage to match increased mass.
• One or more sources of radio frequency energy, used to energize the cylindrical electrodes. A very high power accelerator will use one source for each electrode. The sources must operate at precise power, frequency and phase appropriate to the particle type to be accelerated to obtain maximum device power.

Quadrupole magnets surrounding the linac of the Australian Synchrotron are used to help focus the electron beam

• An appropriate target. If electrons are accelerated to produce X-rays then a water cooled tungsten target is used. Various target materials are used when protons or other nuclei are accelerated, depending upon the specific investigation. For particle-to-particle collision investigations the beam may be directed to a pair of storage rings, with the particles kept within the ring by magnetic fields. The beams may then be extracted from the storage rings to create head on particle collisions.

As the particle bunch passes through the tube it is unaffected (the tube acts as a Faraday cage), while the frequency of the driving signal and the spacing of the gaps between electrodes are designed so that the maximum voltage differential appears as the particle crosses the gap. This accelerates the particle, imparting energy to it in the form of increased velocity. At speeds near the speed of light, the incremental velocity increase will be small, with the energy appearing as an increase in the mass of the particles. In portions of the accelerator where this occurs, the tubular electrode lengths will be almost constant.

• Additional magnetic or electrostatic lens elements may be included to ensure that the beam remains in the center of the pipe and its electrodes.
• Very long accelerators may maintain a precise alignment of their components through the use of servo systems guided by a laser beam.

Advantages

The Stanford University superconducting linear accelerator, housed on campus below the Hansen Labs until 2007. This facility is separate from SLAC

Steel casting undergoing x-ray using the linear accelerator at Goodwin Steel Castings Ltd

Linacs of appropriate design are capable of accelerating heavy ions to energies exceeding those available in ring-type accelerators, which are limited by the strength of the magnetic fields required to maintain the ions on a curved path. High power linacs are also being developed for production of electrons at relativistic speeds, required since fast electrons traveling in an arc will lose energy through synchrotron radiation; this limits the maximum power that can be imparted to electrons in a synchrotron of given size. Linacs are also capable of prodigious output, producing a nearly continuous stream of particles, whereas a synchrotron will only periodically raise the particles to sufficient energy to merit a "shot" at the target. (The burst can be held or stored in the ring at energy to give the experimental electronics time to work, but the average output current is still limited.) The high density of the output makes the linac particularly attractive for use in loading storage ring facilities with particles in preparation for particle to particle collisions. The high mass output also makes the device practical for the production of antimatter particles, which are generally difficult to obtain, being only a small fraction of a target's collision products. These may then be stored and further used to study matter-antimatter annihilation.

Medical linacs

 Flash Back image showing Gordon Isaacs, the first patient treated for retinoblastoma with linear accelerator radiation therapy (in this case an electron beam), in 1957, in the U.S. Other patients had been treated by linac for other diseases since 1953. Gordon's right eye was removed on January 11, 1957 because cancer had spread there. His left eye, however, had only a localized tumor that prompted Henry Kaplan to treat it with the electron beam.

Linac-based radiation therapy for cancer therapy began with treatment of the first patient in 1953 in London at Hammersmith Hospital, with an 8 MV machine built by Metropolitan-Vickers, as the first dedicated medical linac. A short while later in 1955, 6 MV linac therapy from a different machine was being used in the United States.
Medical grade linacs accelerate electrons using a tuned-cavity waveguide, in which the RF power creates a standing wave. Some linacs have short, vertically mounted waveguides, while higher energy machines tend to have a horizontal, longer waveguide and a bending magnet to turn the beam vertically towards the patient. Medical linacs use monoenergetic electron beams between 4 and 25 MeV, giving an X-ray output with a spectrum of energies up to and including the electron energy when the electrons are directed at a high-density (such as tungsten) target. The electrons or X-rays can be used to treat both benign and malignant disease. The LINAC produces a reliable, flexible and accurate radiation beam. The versatility of LINAC is a potential advantage over cobalt therapy as a treatment tool. In addition, the device can simply be powered off when not in use; there is no source requiring heavy shielding – although the treatment room itself requires considerable shielding of the walls, doors, ceiling etc. to prevent escape of scattered radiation. Prolonged use of high powered (>18 MeV) machines can induce a significant amount of radiation within the metal parts of the head of the machine after power to the machine has been removed (i.e. they become an active source and the necessary precautions must be observed).

Application for medical isotope development

The expected shortages with regard to Mo-99, and the technetium-99m medical isotope obtained from it, has also shed light onto linear accelerator technology to produce Mo-99 from non-enriched Uranium-235 through neutron bombardment. This would enable the medical isotope industry to manufacture this crucial isotope by a sub-critical process. The aging facilities, for example the Chalk River Laboratories in Ontario Canada, which still now produce most Mo-99 from highly enriched Uranium-235 could be replaced by this new process. In this way, the sub-critical loading of soluble uranium salts in heavy water with subsequent photo neutron bombardment and extraction of the target product, Mo-99, will be achieved.

Disadvantages

• The device length limits the locations where one may be placed.
• A great number of driver devices and their associated power supplies are required, increasing the construction and maintenance expense of this portion.
• If the walls of the accelerating cavities are made of normally conducting material and the accelerating fields are large, the wall resistivity converts electric energy into heat quickly. On the other hand, superconductors also need constant cooling to keep them below their critical temperature, and the accelerating fields are limited by quenches. Therefore, high energy accelerators such as SLAC, still the longest in the world (in its various generations), are run in short pulses, limiting the average current output and forcing the experimental detectors to handle data coming in short bursts

Accelerator physics
Accelerator physics is a branch of applied physics, concerned with designing, building and operating particle accelerators. As such, it can be described as the study of motion, manipulation and observation of relativistic charged particle beams and their interaction with accelerator structures by electromagnetic fields.
It is also related to other fields:

• Microwave engineering (for acceleration/deflection structures in the radio frequency range).
• Optics with an emphasis on geometrical optics (beam focusing and bending) and laser physics (laser-particle interaction).
• Computer technology with an emphasis on digital signal processing; e.g., for automated manipulation of the particle beam.

The experiments conducted with particle accelerators are not regarded as part of accelerator physics, but belong (according to the objectives of the experiments) to, e.g., particle physics, nuclear physics, condensed matter physics or materials physics. The types of experiments done at a particular accelerator facility are determined by characteristics of the generated particle beam such as average energy, particle type, intensity, and dimensions.

Acceleration and interaction of particles with RF structures

While it is possible to accelerate charged particles using electrostatic fields, like in a Cockcroft-Walton voltage multiplier, this method has limits given by electrical breakdown at high voltages. Furthermore, due to electrostatic fields being conservative, the maximum voltage limits the kinetic energy that is applicable to the particles.
To circumvent this problem, linear particle accelerators operate using time-varying fields. To control this fields using hollow macroscopic structures through which the particles are passing (wavelength restrictions), the frequency of such acceleration fields is located in the radio frequency region of the electromagnetic spectrum.
The space around a particle beam is evacuated to prevent scattering with gas atoms, requiring it to be enclosed in a vacuum chamber (or beam pipe). Due to the strong electromagnetic fields that follow the beam, it is possible for it to interact with any electrical impedance in the walls of the beam pipe. This may be in the form of a resistive impedance (i.e., the finite resistivity of the beam pipe material) or an inductive/capacitive impedance (due to the geometric changes in the beam pipe's cross section).
These impedances will induce wakefields (a strong warping of the electromagnetic field of the beam) that can interact with later particles. Since this interaction may have negative effects, it is studied to determine its magnitude, and to determine any actions that may be taken to mitigate it.                                                              

Superconducting niobium cavity for acceleration of ultrarelativistic particles from the TESLA project

Beam dynamics

Due to the high velocity of the particles, and the resulting Lorentz force for magnetic fields, adjustments to the beam direction are mainly controlled by magnetostatic fields that deflect particles. In most accelerator concepts (excluding compact structures like the cyclotron or betatron), these are applied by dedicated electromagnets with different properties and functions. An important step in the development of these types of accelerators was the understanding of strong focusing. Dipole magnets are used to guide the beam through the structure, while quadrupole magnets are used for beam focusing, and sextupole magnets are used for correction of dispersion effects.
A particle on the exact design trajectory (or design orbit) of the accelerator only experiences dipole field components, while particles with transverse position deviation ${\displaystyle \scriptstyle x(s)}$ are re-focused to the design orbit. For preliminary calculations, neglecting all fields components higher than quadrupolar, an inhomogenic Hill differential equation

${\displaystyle {\frac {d^{2}}{ds^{2}}}\,x(s)+k(s)\,x(s)={\frac {1}{\rho }}\,{\frac {\Delta p}{p}}}$

can be used as an approximation, with

a non-constant focusing force ${\displaystyle \scriptstyle k(s)}$, including strong focusing and weak focusing effects

the relative deviation from the design beam impulse ${\displaystyle \scriptstyle \Delta p/p}$

the trajectory radius of curvature ${\displaystyle \scriptstyle \rho }$, and

the design path length ${\displaystyle \scriptstyle s}$,

thus identifying the system as a parametric oscillator. Beam parameters for the accelerator can then be calculated using Ray transfer matrix analysis; e.g., a quadrupolar field is analogous to a lens in geometrical optics, having similar properties regarding beam focusing (but obeying Earnshaw's theorem).
The general equations of motion originate from relativistic Hamiltonian mechanics, in almost all cases using the Paraxial approximation. Even in the cases of strongly nonlinear magnetic fields, and without the paraxial approximation, a Lie transform may be used to construct an integrator with a high degree of accuracy.

Modeling Codes

There are many different software packages available for modeling the different aspects of accelerator physics. One must model the elements that create the electric and magnetic fields, and then one must model the charged particle evolution within those fields. A popular code for beam dynamics, designed by CERN is MAD, or Methodical Accelerator Design.

Beam diagnostics

A vital component of any accelerator are the diagnostic devices that allow various properties of the particle bunches to be measured.
A typical machine may use many different types of measurement device in order to measure different properties. These include (but are not limited to) Beam Position Monitors (BPMs) to measure the position of the bunch, screens (fluorescent screens, Optical Transition Radiation (OTR) devices) to image the profile of the bunch, wire-scanners to measure its cross-section, and toroids or ICTs to measure the bunch charge (i.e., the number of particles per bunch).
While many of these devices rely on well understood technology, designing a device capable of measuring a beam for a particular machine is a complex task requiring much expertise. Not only is a full understanding of the physics of the operation of the device necessary, but it is also necessary to ensure that the device is capable of measuring the expected parameters of the machine under consideration.
Success of the full range of beam diagnostics often underpins the success of the machine as a whole.

Machine tolerances

Errors in the alignment of components, field strength, etc., are inevitable in machines of this scale, so it is important to consider the tolerances under which a machine may operate.
Engineers will provide the physicists with expected tolerances for the alignment and manufacture of each component to allow full physics simulations of the expected behaviour of the machine under these conditions. In many cases it will be found that the performance is degraded to an unacceptable level, requiring either re-engineering of the components, or the invention of algorithms that allow the machine performance to be 'tuned' back to the design level.
This may require many simulations of different error conditions in order to determine the relative success of each tuning algorithm, and to allow recommendations for the collection of algorithms to be deployed on the real machine.
                                                         Particle accelerator

Sketch of an electrostatic Van de Graaff accelerator

Sketch of the Ising/Widerøe linear accelerator concept, employing oscillating fields (1928)

A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to nearly light speed and to contain them in well-defined beams.
Large accelerators are used in particle physics as colliders (e.g., the LHC at CERN, KEKB at KEK in Japan, RHIC at Brookhaven National Laboratory, and Tevatron at Fermilab), or as synchrotron light sources for the study of condensed matter physics. Smaller particle accelerators are used in a wide variety of applications, including particle therapy for oncological purposes, radioisotope production for medical diagnostics, ion implanters for manufacture of semiconductors, and accelerator mass spectrometers for measurements of rare isotopes such as radiocarbon. There are currently more than 30,000 accelerators in operation around the world.
There are two basic classes of accelerators: electrostatic and electrodynamic (or electromagnetic) accelerators.  Electrostatic accelerators use static electric fields to accelerate particles. The most common types are the Cockcroft–Walton generator and the Van de Graaff generator. A small-scale example of this class is the cathode ray tube in an ordinary old television set. The achievable kinetic energy for particles in these devices is determined by the accelerating voltage, which is limited by electrical breakdown. Electrodynamic or electromagnetic accelerators, on the other hand, use changing electromagnetic fields (either magnetic induction or oscillating radio frequency fields) to accelerate particles. Since in these types the particles can pass through the same accelerating field multiple times, the output energy is not limited by the strength of the accelerating field. This class, which was first developed in the 1920s, is the basis for most modern large-scale accelerators.
Rolf Widerøe, Gustav Ising, Leó Szilárd, Max Steenbeck, and Ernest Lawrence are considered pioneers of this field, conceiving and building the first operational linear particle accelerator, the betatron, and the cyclotron.
Because colliders can give evidence of the structure of the subatomic world, accelerators were commonly referred to as atom smashers in the 20th century. Despite the fact that most accelerators (but not ion facilities) actually propel subatomic particles, the term persists in popular usage when referring to particle accelerators in general.

Uses

Beamlines leading from the Van de Graaff accelerator to various experiments, in the basement of the Jussieu Campus in Paris.

Breakdown of the cumulative number of industrial particle accelerators according to their applications.

The now disused Koffler particle accelerator at the Weizmann Institute, Rehovot, Israel.

Beams of high-energy particles are useful for fundamental and applied research in the sciences, and also in many technical and industrial fields unrelated to fundamental research. It has been estimated that there are approximately 30,000 accelerators worldwide. Of these, only about 1% are research machines with energies above 1 GeV, while about 44% are for radiotherapy, 41% for ion implantation, 9% for industrial processing and research, and 4% for biomedical and other low-energy research. The bar graph shows the breakdown of the number of industrial accelerators according to their applications. The numbers are based on 2012 statistics available from various sources, including production and sales data published in presentations or market surveys, and data provided by a number of manufacturers.

High-energy physics

For the most basic inquiries into the dynamics and structure of matter, space, and time, physicists seek the simplest kinds of interactions at the highest possible energies. These typically entail particle energies of many GeV, and the interactions of the simplest kinds of particles: leptons (e.g. electrons and positrons) and quarks for the matter, or photons and gluons for the field quanta. Since isolated quarks are experimentally unavailable due to color confinement, the simplest available experiments involve the interactions of, first, leptons with each other, and second, of leptons with nucleons, which are composed of quarks and gluons. To study the collisions of quarks with each other, scientists resort to collisions of nucleons, which at high energy may be usefully considered as essentially 2-body interactions of the quarks and gluons of which they are composed. Thus elementary particle physicists tend to use machines creating beams of electrons, positrons, protons, and antiprotons, interacting with each other or with the simplest nuclei (e.g., hydrogen or deuterium) at the highest possible energies, generally hundreds of GeV or more.
The largest and highest energy particle accelerator used for elementary particle physics is the Large Hadron Collider (LHC) at CERN, operating since 2009.

Nuclear physics and isotope production

Nuclear physicists and cosmologists may use beams of bare atomic nuclei, stripped of electrons, to investigate the structure, interactions, and properties of the nuclei themselves, and of condensed matter at extremely high temperatures and densities, such as might have occurred in the first moments of the Big Bang. These investigations often involve collisions of heavy nuclei – of atoms like iron or gold – at energies of several GeV per nucleon. The largest such particle accelerator is the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory.
Particle accelerators can also produce proton beams, which can produce proton-rich medical or research isotopes as opposed to the neutron-rich ones made in fission reactors; however, recent work has shown how to make ⁹⁹Mo, usually made in reactors, by accelerating isotopes of hydrogen,although this method still requires a reactor to produce tritium. An example of this type of machine is LANSCE at Los Alamos.

Synchrotron radiation

Besides being of fundamental interest, electrons accelerated in the magnetic field causes the high energy electrons to emit extremely bright and coherent beams of high energy photons via synchrotron radiation in the continuous spectrum, which have numerous uses in the study of atomic structure, chemistry, condensed matter physics, biology, and technology. A large number of synchrotron light sources exist worldwide. Examples in the US are SSRL and LCLS at SLAC National Accelerator Laboratory, APS at Argonne National Laboratory, ALS at Lawrence Berkeley National Laboratory, and NSLS at Brookhaven National Laboratory. The ESRF in Grenoble, France has been used to extract detailed 3-dimensional images of insects trapped in amber. Thus there is a great demand for electron accelerators of moderate (GeV) energy and high intensity.

Low-energy machines and particle therapy

Everyday examples of particle accelerators are cathode ray tubes found in television sets and X-ray generators. These low-energy accelerators use a single pair of electrodes with a DC voltage of a few thousand volts between them. In an X-ray generator, the target itself is one of the electrodes. A low-energy particle accelerator called an ion implanter is used in the manufacture of integrated circuits.
At lower energies, beams of accelerated nuclei are also used in medicine as particle therapy, for the treatment of cancer.
DC accelerator types capable of accelerating particles to speeds sufficient to cause nuclear reactions are Cockcroft-Walton generators or voltage multipliers, which convert AC to high voltage DC, or Van de Graaff generators that use static electricity carried by belts.

Electrostatic particle accelerators

A Cockcroft-Walton generator (Philips, 1937), residing in Science Museum (London).

 

A 1960s single stage 2 MeV linear Van de Graaff accelerator, here opened for maintenance

Historically, the first accelerators used simple technology of a single static high voltage to accelerate charged particles. The charged particle was accelerated through an evacuated tube with an electrode at either end, with the static potential across it. Since the particle passed only once through the potential difference, the output energy was limited to the accelerating voltage of the machine. While this method is still extremely popular today, with the electrostatic accelerators greatly out-numbering any other type, they are more suited to lower energy studies owing to the practical voltage limit of about 1 MV for air insulated machines, or 30 MV when the accelerator is operated in a tank of pressurized gas with high dielectric strength, such as sulfur hexafluoride. In a tandem accelerator the potential is used twice to accelerate the particles, by reversing the charge of the particles while they are inside the terminal. This is possible with the acceleration of atomic nuclei by using anions (negatively charged ions), and then passing the beam through a thin foil to strip electrons off the anions inside the high voltage terminal, converting them to cations (positively charged ions), which are accelerated again as they leave the terminal.
The two main types of electrostatic accelerator are the Cockcroft-Walton accelerator, which uses a diode-capacitor voltage multiplier to produce high voltage, and the Van de Graaff accelerator, which uses a moving fabric belt to carry charge to the high voltage electrode. Although electrostatic accelerators accelerate particles along a straight line, the term linear accelerator is more often used for accelerators that employ oscillating rather than static electric fields.

Electrodynamic (electromagnetic) particle accelerators

Due to the high voltage ceiling imposed by electrical discharge, in order to accelerate particles to higher energies, techniques involving dynamic fields rather than static fields are used. Electrodynamic acceleration can arise from either of two mechanisms: non-resonant magnetic induction, or resonant circuits or cavities excited by oscillating RF fields.  Electrodynamic accelerators can be linear, with particles accelerating in a straight line, or circular, using magnetic fields to bend particles in a roughly circular orbit.

Magnetic Induction Accelerators

Magnetic induction accelerators accelerate particles by induction from an increasing magnetic field, as if the particles were the secondary winding in a transformer. The increasing magnetic field creates a circulating electric field which can be configured to accelerate the particles. Induction accelerators can be either linear or circular.

Linear Induction Accelerators

Linear induction accelerators utilize ferrite-loaded, non-resonant induction cavities. Each cavity can be thought of as two large washer-shaped disks connected by an outer cylindrical tube. Between the disks is a ferrite toroid. A voltage pulse applied between the two disks causes an increasing magnetic field which inductively couples power into the charged particle beam.
The linear induction accelerator was invented by Christofilos in the 1960s. Linear induction accelerators are capable of accelerating very high beam currents (>1000 A) in a single short pulse. They have been used to generate X-rays for flash radiography (e.g. DARHT at LANL), and have been considered as particle injectors for magnetic confinement fusion and as drivers for free electron lasers.

Betatrons

The Betatron is circular magnetic induction accelerator, invented by Donald Kerst in 1940 for accelerating electrons. The concept originates ultimately from Norwegian-German scientist Rolf Widerøe. These machines, like synchrotrons, use a donut-shaped ring magnet (see below) with a cyclically increasing B field, but accelerate the particles by induction from the increasing magnetic field, as if they were the secondary winding in a transformer, due to the changing magnetic flux through the orbit.
Achieving constant orbital radius while supplying the proper accelerating electric field requires that the magnetic flux linking the orbit be somewhat independent of the magnetic field on the orbit, bending the particles into a constant radius curve. These machines have in practice been limited by the large radiative losses suffered by the electrons moving at nearly the speed of light in a relatively small radius orbit.

Segment of an electron synchrotron at DESY

Electron synchrotrons

Circular electron accelerators fell somewhat out of favor for particle physics around the time that SLAC's linear particle accelerator was constructed, because their synchrotron losses were considered economically prohibitive and because their beam intensity was lower than for the unpulsed linear machines. The Cornell Electron Synchrotron, built at low cost in the late 1970s, was the first in a series of high-energy circular electron accelerators built for fundamental particle physics, the last being LEP, built at CERN, which was used from 1989 until 2000.
A large number of electron synchrotrons have been built in the past two decades, as part of synchrotron light sources that emit ultraviolet light and X rays; see below.

Storage rings

For some applications, it is useful to store beams of high energy particles for some time (with modern high vacuum technology, up to many hours) without further acceleration. This is especially true for colliding beam accelerators, in which two beams moving in opposite directions are made to collide with each other, with a large gain in effective collision energy. Because relatively few collisions occur at each pass through the intersection point of the two beams, it is customary to first accelerate the beams to the desired energy, and then store them in storage rings, which are essentially synchrotron rings of magnets, with no significant RF power for acceleration.

Synchrotron radiation sources

Some circular accelerators have been built to deliberately generate radiation (called synchrotron light) as X-rays also called synchrotron radiation, for example the Diamond Light Source which has been built at the Rutherford Appleton Laboratory in England or the Advanced Photon Source at Argonne National Laboratory in Illinois, USA. High-energy X-rays are useful for X-ray spectroscopy of proteins or X-ray absorption fine structure (XAFS), for example.
Synchrotron radiation is more powerfully emitted by lighter particles, so these accelerators are invariably electron accelerators. Synchrotron radiation allows for better imaging as researched and developed at SLAC's SPEAR.

FFAG accelerators

Fixed-Field Alternating Gradient accelerators (FFAG)s, in which a magnetic field which is fixed in time, but with a radial variation to achieve strong focusing, allows the beam to be accelerated with a high repetition rate but in a much smaller radial spread than in the cyclotron case. Isochronous FFAGs, like isochronous cyclotrons, achieve continuous beam operation, but without the need for a huge dipole bending magnet covering the entire radius of the orbits. Some new developments in FFAG accelerators are covered in .

Flash Back

Ernest Lawrence's first cyclotron was a mere 4 inches (100 mm) in diameter. Later, in 1939, he built a machine with a 60-inch diameter pole face, and planned one with a 184-inch diameter in 1942, which was, however, taken over for World War II-related work connected with uranium isotope separation; after the war it continued in service for research and medicine over many years.
The first large proton synchrotron was the Cosmotron at Brookhaven National Laboratory, which accelerated protons to about 3 GeV (1953–1968). The Bevatron at Berkeley, completed in 1954, was specifically designed to accelerate protons to sufficient energy to create antiprotons, and verify the particle-antiparticle symmetry of nature, then only theorized. The Alternating Gradient Synchrotron (AGS) at Brookhaven (1960–) was the first large synchrotron with alternating gradient, "strong focusing" magnets, which greatly reduced the required aperture of the beam, and correspondingly the size and cost of the bending magnets. The Proton Synchrotron, built at CERN (1959–), was the first major European particle accelerator and generally similar to the AGS.
The Stanford Linear Accelerator, SLAC, became operational in 1966, accelerating electrons to 30 GeV in a 3 km long waveguide, buried in a tunnel and powered by hundreds of large klystrons. It is still the largest linear accelerator in existence, and has been upgraded with the addition of storage rings and an electron-positron collider facility. It is also an X-ray and UV synchrotron photon source.
The Fermilab Tevatron has a ring with a beam path of 4 miles (6.4 km). It has received several upgrades, and has functioned as a proton-antiproton collider until it was shut down due to budget cuts on September 30, 2011. The largest circular accelerator ever built was the LEP synchrotron at CERN with a circumference 26.6 kilometers, which was an electron/positron collider. It achieved an energy of 209 GeV before it was dismantled in 2000 so that the underground tunnel could be used for the Large Hadron Collider (LHC). The LHC is a proton collider, and currently the world's largest and highest-energy accelerator, achieving 6.5 TeV energy per beam (13 TeV in total).
The aborted Superconducting Super Collider (SSC) in Texas would have had a circumference of 87 km. Construction was started in 1991, but abandoned in 1993. Very large circular accelerators are invariably built in underground tunnels a few metres wide to minimize the disruption and cost of building such a structure on the surface, and to provide shielding against intense secondary radiations that occur, which are extremely penetrating at high energies.
Current accelerators such as the Spallation Neutron Source, incorporate superconducting cryomodules. The Relativistic Heavy Ion Collider, and Large Hadron Collider also make use of superconducting magnets and RF cavity resonators to accelerate particles.

Targets and detectors

The output of a particle accelerator can generally be directed towards multiple lines of experiments, one at a given time, by means of a deviating electromagnet. This makes it possible to operate multiple experiments without needing to move things around or shutting down the entire accelerator beam. Except for synchrotron radiation sources, the purpose of an accelerator is to generate high-energy particles for interaction with matter.
This is usually a fixed target, such as the phosphor coating on the back of the screen in the case of a television tube; a piece of uranium in an accelerator designed as a neutron source; or a tungsten target for an X-ray generator. In a linac, the target is simply fitted to the end of the accelerator. The particle track in a cyclotron is a spiral outwards from the centre of the circular machine, so the accelerated particles emerge from a fixed point as for a linear accelerator.
For synchrotrons, the situation is more complex. Particles are accelerated to the desired energy. Then, a fast acting dipole magnet is used to switch the particles out of the circular synchrotron tube and towards the target.
A variation commonly used for particle physics research is a collider, also called a storage ring collider. Two circular synchrotrons are built in close proximity – usually on top of each other and using the same magnets (which are then of more complicated design to accommodate both beam tubes). Bunches of particles travel in opposite directions around the two accelerators and collide at intersections between them. This can increase the energy enormously; whereas in a fixed-target experiment the energy available to produce new particles is proportional to the square root of the beam energy, in a collider the available energy is linear.

Higher energies

A Livingston chart depicting progress in collision energy through 2010. The LHC is the largest collision energy to date, but also represents the first break in the log-linear trend.

At present the highest energy accelerators are all circular colliders, but both hadron accelerators and electron accelerators are running into limits. Higher energy hadron and ion cyclic accelerators will require accelerator tunnels of larger physical size due to the increased beam rigidity.
For cyclic electron accelerators, a limit on practical bend radius is placed by synchrotron radiation losses and the next generation will probably be linear accelerators 10 times the current length. An example of such a next generation electron accelerator is the proposed 40 km long International Linear Collider.
It is believed that plasma wakefield acceleration in the form of electron-beam 'afterburners' and standalone laser pulsers might be able to provide dramatic increases in efficiency over RF accelerators within two to three decades. In plasma wakefield accelerators, the beam cavity is filled with a plasma (rather than vacuum). A short pulse of electrons or laser light either constitutes or immediately precedes the particles that are being accelerated. The pulse disrupts the plasma, causing the charged particles in the plasma to integrate into and move toward the rear of the bunch of particles that are being accelerated. This process transfers energy to the particle bunch, accelerating it further, and continues as long as the pulse is coherent.
Energy gradients as steep as 200 GeV/m have been achieved over millimeter-scale distances using laser pulsers and gradients approaching 1 GeV/m are being produced on the multi-centimeter-scale with electron-beam systems, in contrast to a limit of about 0.1 GeV/m for radio-frequency acceleration alone. Existing electron accelerators such as SLAC could use electron-beam afterburners to greatly increase the energy of their particle beams, at the cost of beam intensity. Electron systems in general can provide tightly collimated, reliable beams; laser systems may offer more power and compactness. Thus, plasma wakefield accelerators could be used – if technical issues can be resolved – to both increase the maximum energy of the largest accelerators and to bring high energies into university laboratories and medical centres.
Higher than 0.25 GeV/m gradients have been achieved by a dielectric laser accelerator, which may present another viable approach to building compact high-energy accelerators.

Accelerator operator

An accelerator operator controls the operation of a particle accelerator used in research experiments, reviews an experiment schedule to determine experiment parameters specified by an experimenter (physicist), adjust particle beam parameters such as aspect ratio, current intensity, and position on target, communicates with and assists accelerator maintenance personnel to ensure readiness of support systems, such as vacuum, magnet power supplies and controls, low conductivity water (LCW) cooling, and radiofrequency power supplies and controls. Additionally, the accelerator operator maintains a record of accelerator related events.


            
   XXX  .  XXX 4%zero null 0 1 2  Stabilization of a cold cathode electron beam glow discharge
                                                           for surface treatment 


We have demonstrated that the reproducibility of electron beam pulses generated by a high power, cold cathode glow discharge is greatly improved by adding a small continuous keep-alive discharge current. A current of the order of 200 μA was found to limit the shot to shot current variation to within 1.5%. This stabilization in turn reduces by an order of magnitude the fluctuations of the energy density deposited on the target, demonstrating a reliable energy source for surface treatment.

Feedback control of quantum mechanical systems is rapidly attracting attention not only due to fundamental questions about quantum measurements, but also because of its novel applications in many fields in physics. Quantum control has been studied intensively in quantum optics but progress has recently been made in the control of solid-state qubits as well. In quantum transport only a few active and passive feedback experiments have been realized on the level of single electrons, although theoretical proposals exist. Here we demonstrate the suppression of shot noise in a single-electron transistor using an exclusively electronic closed-loop feedback to monitor and adjust the counting statistics. With increasing feedback response we observe a stronger suppression and faster freezing of charge current fluctuations. Our technique is analogous to the generation of squeezed light with in-loop photo detection as used in quantum optics. Sub-Poisson single-electron sources will pave the way for high-precision measurements in quantum transport similar to optical or optomechanical equivalents.

 

Electron guns

When a piece of metal is heated, electrons escape from its surface. These free electrons can be accelerated in a vacuum, producing a beam. The hot metal surface and the accelerating plates are sometimes called an ‘electron gun’.

In an electron gun, the metal plate is heated by a small filament wire connected to a low voltage. Some electrons (the conduction electrons) are free to move in the metal – they are not bound to ions in the lattice. As the lattice is heated, the electrons gain kinetic energy. Some of them gain enough kinetic energy to escape from the metal surface. We sometimes say that they are ‘boiled off’ the surface or ‘evaporate’ from it. Although they do not form a gas in the strictest sense, these are good descriptions.

 

If the hot metal plate is in a vacuum, then the evaporated electrons are free to move. The electrons can be pulled away from the hot surface of the plate by putting a positive electrode (anode) nearby. The anode is created by connecting an electrode to the positive terminal of a power supply, and the hot plate is connected to its negative terminal. The hot plate is then the cathode.

As soon as the electrons evaporate from the surface of the hot plate, they are pulled towards the anode. They accelerate and crash into the anode. However, if there is a small hole in the anode, some electrons will pass through, forming a beam of electrons that came from the cathode – or a cathode ray.

This cathode ray can be focused and deflected and can carry small 

 

currents. This is the basis of the important experiments carried out by J J Thomson and others. It is also the basis of early electronic devices.

You could explain the operation of an electron gun thus:
 

• At one end of the tube there is a little rocket shaped 'gun'. In that gun a starting plate is heated by a tiny electric grill. The plate has a special surface that lets electrons loose rather easily. Electrons come off that plate. They are speeded up in the gun by a large potential difference between that starting plate (‘negative cathode’) and the gun muzzle (‘positive anode’).

 

     Electrons come out at high speed through a tiny hole in the cone-shaped muzzle. 

The electrons continue at that constant speed through the vacuum because there is nothing for them to collide with - until they hit a fluorescent screen, where they make a bright spot. 

The glass globe of the tube has been pumped out to a very good vacuum, removing air which would soon slow down electrons by collisions. But then a very little helium (or hydrogen) gas is let in. Because the helium atoms give out a green glow when hit by electron, you can see the path of the electrons made visible as a thin line of glow. (Hydrogen glows blue.) 

Look at the thin glowing line carefully. You are seeing the path of electrons flying through thin helium (or hydrogen), almost a vacuum, all by themselves, with no wires there. 

Focusing
The fine beam tube is improved by adding a small conical electrode – often connected to the anode. This produces a converging electric field which focuses the electrons and produces a tighter beam and sharper spot on the fluorescent screen.

                     XXX  .  XXX 4%zero null 0 1 2 3 4 Electronic circuit Electron Gun

                                                                      

                                        

 

                         

 

                         

                         

                        

 

                         

                                                

                            

       A small ultrasonic cleaning device and it runs 1 x 50W transducer at the moment. I am going to build another that uses two 20W transducers and was just wondering what the best configuration is, to wire them in series or in parallel My circuit designs should be regarded as experimental. Although they work in simulation, their component values may need altering .

or additional components may be necessary when the circuits are built. Due safety precautions should be taken with any circuit involving mains voltage or electrostatic-sensitive components. You are going to have to position your transducers at very precise distances from each other to avoid them canceling one another out. It depends on the impedance of the 20watt unit compared to the 50watt unit, you do need to impedance match, I`m thinking series is probably the way to go, With the Ohms at 30 per 20W parallel would make it 15 Ohms which is probably closer to the 20 Ohms of the standard transducer as opposed to series that would make it 60 Ohms .

 

                                                                Stun Gun Circuit

A stun gun is a gadget used to produce a high voltage, low current signal, used mostly as a weapon to stun or send shock waves to the target with the intention to weaken or paralyze it. However proceeding to design the circuit, it should be kept in mind that in some countries, stun gun is banned. Because, this is actually a lethal weapon which can render a person mentally paralyzed. It is usually powered by a 9V battery. Here, we design a stun gun circuit using a 555 Timer to produce a current fluctuating signal and a voltage multiplier using a transformer and a multiple stage arrangement of voltage doublers using capacitors and diodes.

Stun Gun Circuit Operating Principle:

The stun gun circuit is based on the principle behind a conventional stun gun. A 555 Timer is used to produce an oscillating signal of frequency determined by the external passive elements connected to the Timer. These low current electric pulses are fed to a step up transformer to produce a high volt signal, which is further increased by a voltage multiplier circuit. The voltage multiplier circuit consists of multiple stages of voltage doubler each consisting of two diodes and two capacitors. The voltage doubler circuits are based on Villard doubler method. Output voltage is directly proportional to the number of stages.

Stun Gun Circuit Diagram:

Circuit Diagram of Stun Gun

 

 

Stun Gun Circuit Design:

Actually, here we require two phases of designing – The astable multivibrator design and voltage multiplier design.
Designing the circuit requires pioneer step of deciding the output voltage . Here our requirement is to generate a 10KV DC voltage from 1000V input.
From the equation,
V_out = (2V_in + 1.414)S, where S is the number of stages.
To obtain voltage of 10KV, about 5 stages of voltage doubler would be required.
Here we design a 5 stage voltage multiplier circuit generating an output voltage of 10KV.  Since input voltage is around 1000v, each capacitor should have a voltage rating of atleast 1000V. Since here operating frequency is low, of the order of Hertz, we require a 2500V, 10mF.
For designing the astable multivibrator circuit, we select a 555 Timer. To design a 555 Timer in astable mode, passive external components need to be selected.
Assuming a maximum operating frequency of 50Hz and a duty cycle of 75%, we calculate R1 to be around 1.44K, R2 around 720 Ohms and C₁ around 10uF. Here we select a 2K potentiometer, 720 ohm resistor and 10uF capacitor. Since this is a low frequency operation, a MOSFET IRF530 is used.

How to Operate Stun Gun Circuit?

As soon as the switch S1 is pressed, the astable operation of 555 Timer starts. A pulsating electric signal of low current is produced, which is stepped up using a step up transformer, to a voltage of around 1000V. The signal from the Timer is fed through a MOSFET switch.

1. During first positive half cycle, capacitor C3 charges through diode D1, which is forward biased. Since the capacitor has no discharge path, it stores the charge. This produces a voltage equal to the AC input peak value at the end of half cycle.
2. During negative half cycle, diode D2 is forward biased and capacitor C4 charges through C3 and D2. At the end of the cycle a voltage equal to double the input AC voltage.
3. Again during next positive half cycle, diode D3 is forward biased and capacitor C5 charges. Again during next half cycle, diode D4 is forward biased and capacitor C6 charges. At the end of the cycle, a voltage equal to 4 times the input peak voltage is obtained at point 2.
4. The same procedure applies for other two stages and finally a voltage equal to 10 times the input voltage is obtained at point 5.

Stun Gun Applications:

1. It can be used for security purpose for individuals from intruders.
2. It can be used as protection from animals.
3. It can be used as modern warfare equipment.

 Limitations of Stun Gun Circuit:

1. Since this involves high voltage pulse production, the circuit is hazardous and should be implemented on hardware with uttermost care and precaution.
2. One should not touch the output with bare hands as this high voltage, low current signal can send shock waves through the body, disrupting the nervous system.
3. While designing the circuit, factors like corona discharge, stray capacitance are not taken into account, which may affect the output.
4. This circuit should never be used in presence of persons with cardiac issues.
5. It is actually to get a 9:1000 step up transformer at low frequency and its construction is quite complex.

The 10:1 transformer is a step down, not step up, and even if it were a 1:10; it would only put out 90V, not 500V. The voltage multiplier equation does not look correct either, but I am not going to specifically attack that one because it can easily be looked up. Additionally, the 75% duty cycle and low frequency seem very wasteful in this project since the MOSFET can easily handle the higher frequencies and the capacitors will have a lower impedance at such frequencies allowing a greater output current. If the low frequency was chosen because of an iron core transformer, it should be replaced with a ferrite core, because it is: more efficient, can handle higher frequencies, is lighter, and more compact for a stun gun. Finally, the transformer does not respond more strongly to a longer duty cycle after a point, so there is definitely wasted input there also. The accompanying paragraphs with this diagram are also not very well written and full of small errors.



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        ELECTRONIC GUN  JUMP OVER TO STUNT GUN GO IN SPACE E _ EYESRAM


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