Abstract:
A device and method for generating pulses to activate and deactivate a kicker magnet is provided. When the kicker magnet is deactivated the circuit generates and stores a magnetic field in an inductor. When the kicker magnet is activated, the circuit changes configuration so that the magnetic field and current stored in the inductor can provide the necessary current to activate the kicker magnet is a minimal amount of time. The configuration of the circuit changes via the use of switches. The switches can employ Zener diodes arranged so as to provide protection against high voltage events and rogue neutrinos that may bombard the switches when the kicker magnet is used in the context of deflecting a particle beam.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 62/295,362, filed Feb. 15, 2016, titled “SYSTEM AND METHOD FOR HIGH POWER PULSE GENERATOR,” which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    This disclosure relates to the generation of high power pulses with a minimal rise time for use in powering devices such as a kicker magnet that require high powered pulses to quickly power a magnet designed to deflect a particle beam away from or towards a target. 
       BACKGROUND OF THE DISCLOSURE 
       [0003]    Directed particle beams can be used in the research, industry, and medical applications to achieve various benefits. As an example, a directed particle beam can be used to ionize cancerous cells thereby changing the characteristics of the cancerous cells and often times hampering the ability of the cancerous cells to proliferate. 
         [0004]    As a safety mechanism, an operator controlling the directed particle beam, must be able to terminate or redirect the particle beam away from a target, often times very quickly. One method to terminate the particle beam is to simply turn it off, however the amount of time needed to turn the beam off can be lengthy, and thus may not prove to be an effective method to remove the beam from impinging upon a target in an emergency situation. 
         [0005]    Quickly redirecting the particle beam away from a target can be an effective way of immediately stopping the beam from impinging upon the body of the target. High power magnets can be employed to redirect the beam. The magnetic field generated by a high power magnet can cause the beam to change its direction through its interaction with the stream of accelerated particles that make up the particle beam. The magnetic field can be used to deflect the beam away from a target. 
         [0006]    In many accelerator applications, requiring a fast-kicker magnet, radiation generated by particle beams, can limit the physical proximity of the modulator to the magnet. Conventionally, the modulator may be located hundreds of feet away from the radiation environment, increasing the complexity and cost of the modulator and cabling. 
         [0007]    Powering up the magnet used to the deflect the beam quickly can be critical due to the fact that during the period of time when the magnetic field is building in the kicker magnet, the beam is only being partially deflected and may begin to impinge on unintended surfaces such as the hardware components associated with the particle beam or other surrounding areas. The particle beam should be deflected away from the target as quickly as possible and this can require that the kicker magnet be powered up quickly (i.e., the amount of time that the circuit has a large applied voltage resulting in a fast current rise should be minimized). Furthermore, given the radiation environment that a particle beam and its associated electronics operate in, the application time of a high voltage should be minimized so as to avoid radiation particles damaging the electronics. 
         [0008]    Given the amount of current and voltage required to generate a magnetic field with enough of strength to deflect a particle beam, a traditional pulse generator may not be adequate due to the high voltage and currents needed to build the magnetic field. A specialized high power pulse generator, in which the components of the generator can handle the magnitude of current and voltage necessary to operate the kicker magnet, while also generating a pulse with a quick rise time can be necessary to effectively operate a kicker magnet. 
       SUMMARY OF THE DISCLOSURE 
       [0009]    Accordingly, a system and method for generating and delivering a high power pulse to a kicker magnet is provided. The system and method can include a circuit configured to store charge in an inductor during a time period when the kicker magnet is not activated. When the kicker is activated, the circuit can be configured such that the charge stored in an inductor is immediately driven into the kicker magnet. The components of the circuit can include protection features such as Zener diodes that ensure that the circuit does not become negatively impacted from anomalies that can be present in the particle-beam high power environment. 
         [0010]    The main susceptibility of pulse generator circuits to radiation-induced failure can be the solid-state switches employed by the circuit that are in an open-state holding off high-voltage. By using an inductively-driven topology to switch DC current flowing through a considerable inductance into the kicker magnet, the time that high-voltage is across the solid-state switch can be minimized and substantially equal to the current rise-time and fall-time in the kicker magnet, thus increasing a mean time to failure (MTTF) of the pulse generator in the radiation environment. 
         [0011]    The complexity of the primary energy source can also be reduced to a low-voltage high-current supply that can be located with the controls away from the radiation and linked by high-current DC cabling. This method can allow for an arbitrary pulse width and rep-rate as well as substantially unlimited DC current in the kicker with minimal droop after the initial fast-rise. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  illustrates an exemplary high power pulse generation circuit according to examples of the disclosure. 
           [0013]      FIG. 2  illustrates an exemplary circuit equivalent of  FIG. 1  when the kicker magnet is in an off state according to examples of the disclosure. 
           [0014]      FIG. 3  illustrates an exemplary circuit equivalent of  FIG. 2  when the kicker magnet is in an on state according to examples of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Described herein are systems and methods for generating high power pulses with fast rise times for use in driving a magnetic load such as that used in a kicker magnet. The systems and methods described herein can be used to ensure that a kicker magnet receives a high powered current pulse with a minimal rise time, when a user of the kicker of the magnet activates the magnet. 
         [0016]    The systems and method employ a circuit that includes a first inductor with a large inductance to build up and store a magnetic field during a time period when the kicker magnet is not being operated. When the kicker magnet is activated, the configuration of the circuit is switched so that the energy stored in the first inductor quickly induces a large voltage across the kicker magnet thereby ensuring that the kicker magnet is activated quickly and with a sufficient current and magnetic field to cause the particle beam to deflect. 
         [0017]      FIG. 1  illustrates an exemplary high power pulse generation circuit according to examples of the disclosure. The circuit  100  can be configured to quickly activate a kicker magnet  124 . Kicker magnet  124  can be a low impedance electro magnet that can re-direct a particle beam once the magnet is activated. The kicker magnet  124  should be activated quickly due to the fact that while the magnetic field is building up in the kicker magnet (during the time that the current through the kicker magnet is rising), the beam may only be partially deflected and will only be completely deflected once the kicker magnet receives the full amount of current. In the example of a high energy particle beam, a partial deflection can place a large amount of energy (heat or radiation) on a party of the accelerator (i.e., a vacuum tube) that may not be able to handle the increased amount of energy. 
         [0018]    In one example, in order to power up quickly, the kicker magnet  124  can require the current flowing through the kicker magnet to increase from 0 amps to 700 in ˜ one microsecond. Due to this requirement, conventional methods of powering up a device may not be sufficient. As an example, simply connecting the kicker magnet to a power source that can drive 700 amps may not be sufficient due to the fact that such methods usually require one millisecond or longer for the current to ramp up. This can be due to the fact that the inductance in the kicker magnet  124  may require a high voltage to be applied to it in order to obtain a fast current rise-time. 
         [0019]    Therefore, circuit  100  can include a system that can drive the kicker magnet  124  with the current it requires at a speed that is required by the system in which the magnet operates. The circuit  100  can be powered by a power source/supply  102  which can generate substantially all of the prime power for the circuit. As an example, the power supply  102  can be configured to generate approximately 12.5 volts at 800 amps so that during operation of the system when the power supply is on, it can be generating the 700 amps required by the kicker magnet  124  can be generated whether or not the kicker magnet has been activated. 
         [0020]    The circuit  100  can include two separate sets of switches. The first set of switches  104 ,  106 ,  108 ,  110 , can connect the power supply  102  to an inductor  120 , during a time period when the kicker magnet has not been activated. Switches  104 ,  106 ,  108 , and  110  can be implemented as transistors (each having a base, collector, and emitter) that are rated for high power applications. While the circuit  100  is shown as including four separate switches, one of skill in the art would recognize that the number of switches could be more or less, and are dependent on the power and voltage ratings of the switches used to implement circuit  100 . In one example, switches  104 ,  106 ,  108 ,  110 ,  112 ,  114 ,  116 , and  118  can be implemented as insulated-gate bipolar (IBGT) transistors. 
         [0021]    The circuit  100  can include a second set of switches  112 ,  114 ,  116 , and  118 . The second set of switches  112 ,  114 ,  108 ,  110 , when activated can connect the power supply  102  and secondary inductor  120  to kicker magnet  124  during a time period with the kicker magnet is activated. Switches  112 ,  114 ,  116 , and  118  can be implemented as transistors (each having a base, collector, and emitter) that are rated for high power applications. While the circuit  100  is shown as including four separate switches, one of skill in the art would recognize that the number of switches could be more or less, and are dependent on the power and voltage ratings of the switches used to implement circuit  100 . 
         [0022]    Using the first and second set of switches, the circuit  100  can be operated in two separate configurations that can be mutually exclusive of one another. In one configuration, the circuit  100  can be configured to charge the secondary inductor  120  during a time period when the kicker magnet has not been activated. In another configuration, the circuit  100  can be configured to transfer the charge stored in the secondary inductor  120  into the kicker magnet  124  during a time period when the kicker magnet has been activated. 
         [0023]      FIG. 2  illustrates an exemplary circuit equivalent of  FIG. 1  when the kicker magnet is in an off state according to examples of the disclosure. The example of  FIG. 2  illustrates the configuration of the circuit  100  of  FIG. 1  when the kicker magnet is an off state. When the kicker magnet  124  is in an off state, switches  112 ,  114 ,  116 , and  118  can be switched off. The switches  112 ,  114 ,  116 , and  118  can be switched off by applying an appropriate amount of voltage to the gates of the voltage using gate drivers  132   a  and  132   b.  The gate drivers  132   a  and  132   b  can provide a voltage necessary to cause switches  112 ,  114 ,  116 , and  118  to not allow current to flow between their respective collectors and emitters. In this way, switches  112 ,  114 ,  116 , and  118  can be effectively open circuits that do not allow current to pass through the switch. In the example of  FIG. 2 , switches  112 ,  114 ,  116 , and  118  are marked with “X”s through them to represent that they are open. 
         [0024]    While switches  112 ,  114 ,  116 , and  118  are open, switches  104 ,  106 ,  108 , and  110  are closed. Gate voltage drivers  132   d  and  132   c  can provide an appropriate voltage to the gates of switches  104 ,  106 ,  108 , and  110  respectively so as to close the switches, thus providing a path to flow between the collector and the emitter of each switch. By establishing current paths through the switches, the current flowing from the power supply  102  can go through the secondary inductor  120 , which can have a large inductance. As an example, secondary inductor  120  can have an inductance of 360 μH. The power supply  102  during this configuration of the circuit  100  can be generating approximately 5 volts at 800 amps. The current generated by the power supply  102  can flow through the secondary inductor  120  and then through the switches  104 ,  106 ,  108 , and  110  before returning to the power supply  102 . 
         [0025]    As described, in the configuration illustrated in  FIG. 2 , the power supply  102  can pump current through secondary inductor  120 . The current flowing through secondary inductor  120  can build up a magnetic field in the inductor. The magnetic field can build in the secondary inductor  120  until the circuit reaches a steady state and the magnetic field in the secondary inductor  120  remains constant. This magnetic field can remain in the secondary inductor  120  until the circuit  100  is switched into the second configuration. 
         [0026]      FIG. 3  illustrates an exemplary circuit equivalent of  FIG. 2  when the kicker magnet is in an on state according to examples of the disclosure. The example of  FIG. 2  can illustrate the configuration of the circuit  100  of  FIG. 1  when the kicker magnet is activated. When the kicker magnet is activated, switches  112 ,  114 ,  116 , and  188  can activate (i.e., a voltage can be applied to their respective gates so as to allow current to flow between the collectors and emitters of each switch), while simultaneously switches  104 ,  106 ,  108 , and  110  can be switched off (i.e., a voltage can be applied to their respective gates so that substantially no current flows between the collectors and emitters of each switch). With switches  104 ,  106 ,  108 , and  110  switched off, those switches effectively act as open circuits (denoted by the “X”s in the figure), while switches  112 ,  114 ,  116 , and  118  can provide a new path for the current generated by power supply  102  to flow. 
         [0027]    After having built up a magnetic field in secondary inductor  120  when the kicker magnet is not active and the circuit is in the configuration discussed with respect to  FIG. 2 , by simultaneously activating switches  112 ,  114 ,  116 , and  118  and deactivating switches  104 ,  106 ,  108 , and  110 , the current flow of the circuit  100  can be rerouted through the active switches and into the kicker magnet  124 . 
         [0028]    As previously discussed, with respect to  FIG. 2  since a 700 amp current was flowing through the secondary inductor in the first configuration, when the configuration of the circuit is changed to the configuration illustrated in  FIG. 3 , the secondary inductor  120  can resist the change of the flow of the current caused by the changing switches, and can generate any voltage across the inductor so as to resist the change in flow of the current. Taking advantage of this fact, the ratio of inductance between the secondary inductor  120  and the inductance in the kicker magnet  124  can be designed so that the secondary inductor  120  produces enough voltage to push 700 amps into the kicker magnet  124  in ˜one microsecond. As mentioned above the secondary inductor  120  can have an inductance value of 360 μH. In order to cause the voltage in the secondary inductor  120  to be high enough when the circuit is switched so as to push 700 amps of current into the kicker magnet  124 , the inductance of the kicker magnet can be configured to be approximately 6.5 μH. By setting the ratio between the inductances of the secondary inductor  120  and the kicker magnet  124  accordingly, when the kicker magnet is activated the voltage on the kicker magnet  124  can be approximately 5000V thus making the current flowing through the kicker magnet  124  approximately 700 A. The rise in voltage and the delivery of current can occur within ˜ a microsecond. 
         [0029]    Once the current through the kicker magnet equals 700 A, which can be the same amount of current flowing through the secondary inductor  120 , the high voltage across the secondary inductor may no longer be needed to maintain the current flow at 700 A and voltage can fall to a minimal value due to the fact that the resistance of the kicker magnet can be small. Thus after the current rises to the desired value in the kicker magnet, the power supply  102  can provide approximately 700 A through the secondary inductor  120 , through switches  112 ,  114 ,  116 , and  118 , through the kicker magnet  124 , and then back to the power supply. 
         [0030]    When an operator of the circuit wishes to turn the kicker magnet off, switches  112 ,  114 ,  116 , and  118  can be opened, while switches  104 ,  106 ,  108 , and  110  can be closed, so that the circuit reverts back to the first configuration described above with respect to  FIG. 2 , and the secondary inductor  120  begins building up a magnetic field. 
         [0031]    By using inductors to drive current rather than using capacitors, the time in which the pulse generator operates at a high voltage can be minimized. In a current driver for a kicker magnet that uses capacitors to store voltage, a capacitor may sit for an indefinite period of time at a high voltage. The voltage can then be transferred through the switch or switches and finally to the kicker magnet. This transfer can generate a high voltage on the kicker magnet that can remain on the kicker magnet for an indefinite amount of time. During this indefinite amount of time, radiation (from the particle beam) may strike the switch due to its proximity to the beam and cause it to erroneously close. This can be especially true since the high voltage across the switch can already be providing pressure for the switch to close. Thus the kicker magnet could potentially be activated without the operator intervention and could cause damage to the system. 
         [0032]    By using inductors instead of capacitors to drive the current, rather than storing voltage, the system stores current. This can allow the circuit to only have high voltage present for the ˜1 μS it takes for the current to rise and fall in the kicker magnet, thus minimizing the chance for radiation to cause a misfire event in a switch. 
         [0033]    When the circuit  100  is switched from the configuration illustrated in  FIG. 2 , to the configuration illustrated in  FIG. 3 , the transient high voltage experienced by the circuit can leave the individual components of the circuit to be susceptible to damage. Specifically, the high voltage can cause the switches  104 ,  106 ,  108 ,  110 ,  112 ,  114 ,  116 , and  118  to become damaged. In order to provide robust protection to the switches, circuit  100  can employ methods to protect the switches. 
         [0034]    Referring back to  FIG. 1 , each switch  104 ,  106 ,  108 ,  110 ,  112 ,  114 ,  116 , and  118  can be configured with a Zener diode  126   a - h  respectively so as to protect the switch from being damaged by high voltage events. Each Zener diode  126   a - h  can connect the collector of each switch to its gate. The breakdown voltage of each Zener diode can be selected to make it suitable for the voltages that the switch attached to diode will likely see during operation of the circuit  100 . Thus, as an example, the Zener diodes  126   e - h  which are attached to switches  112 ,  114 ,  116 , and  118  respectively can be chosen to have a breakdown voltage of approximately 500V. The switches  112 ,  114 ,  116 , and  118  can be rated for 1200V so as to leave a substantial amount of margin between the overall power rating of the switch and the Zener diode breakdown voltage of the diodes used to protect the switch. Thus, during operation of the circuit, should the voltage across the switches  112 ,  114 ,  116 , and  118  exceed 500V when the switches are in off state (i.e., the configuration of  FIG. 2 ), the Zener diodes  126   e - h  can be activated thus turning the gate of each switch back on and causing the switch to conduct. When the switches  112 ,  114 ,  116 , and  118  are forced to conduct by the Zener diodes  126   e - h,  the voltage across each switch can collapse/reduce the voltage across it thereby protecting the switch from damage. 
         [0035]    The Zener diodes  126   a - d  associated with switches  104 ,  106 ,  108  and  110  can operate in substantially the same way. Switches  104 ,  106 ,  108 , and  110  can be rated for 6500V while the Zener diodes  126   a - d  can be chosen to have breakdown voltage of 4 kV thereby providing margin between the rating of the switch and the Zener diode breakdown voltage. In substantially the same manner as discussed above, when the voltage across switches  104 ,  106 ,  108 , and  110  exceeds 4 kV, the Zener diodes  126   a - d  can be activated thereby providing a conducting path between the collector and gates of each switch. The conducting path can be used to collapse/reduce the voltage across each switch thereby providing protection for the circuit. 
         [0036]    As a secondary means of providing protection to the switches in the circuit  100 , each switch  104 ,  106 ,  108 ,  110 ,  112 ,  114 ,  116 , and  118  can have a larger Zener diode  128   a - d  placed across the entire switch. As illustrated in  FIG. 1 , large Zener diode  128   a  can be placed across switches  104  and  106 ,  128   b  can be placed across switches  108  and  110 ,  128   c  can be placed across switches  116  and  118 , and  128   d  can be placed across switches  112  and  114 . The large Zener diodes  128   a - d  can be higher rated than Zener diodes  126   a - h.  As an example, Zener diodes  128   a  and  128   b  can be rated for 5 kV at 700 A while Zener diodes  128   c  and  128   d  can be rated at 600V at 700 A. In this way, should Zener diodes  126   a - h  fail for any reason, the larger Zener diodes can be configured to collapse the voltage across the switch should the need arise. 
         [0037]    In addition to the protection mechanisms described above, the circuit  100  can also include dedicated diagnostic hardware. Referring to  FIG. 1 , the circuit  100  can include current meters  134   a  and  134   b  that can measure the current flowing into kicker magnet  124 . Circuit  100  can also include a voltage divider circuit  136  that can measure the voltage across kicker voltage  124 . These diagnostic instruments can allow for an operator of the circuit  100  to ensure that the kicker magnet  124  is receiving the desired amount of current in the desired amount of time when the kicker magnet is activated. 
         [0038]    The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the techniques and their practical applications. Others skilled in the art are thereby enabled to best utilize the techniques and various embodiments with various modifications as are suited to the particular use contemplated. 
         [0039]    Although the disclosure and examples have been fully described with reference to the accompanying figures, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosure and examples as defined by the claims.