# US 2014/0152197 A1 · Charged Particle Accelerator Systems including Beam Dose and Energy Compensation and Methods Therefor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0152197 A1 - Document ID: US20140152197A1 - Status: Published application - Kind: A1 - Application number: 13/692,344 - Filed: 2012-12-03 - Published: 2014-06-05 - Earliest claimed: 2012-12-03 - Assignees: Varian Medical Systems, Inc. - Applicants: Varian Medical Systems, Inc. - Inventors: Gongyin CHEN; Kenneth Todd Romriell; David Alan Howell - Web page: https://patentgrep.com/patent/US20140152197A1 ## CPC - H05H 7/02: Circuits or systems for supplying or feeding radio-frequency energy - H01J 35/025: {X-ray tubes with structurally associated circuit elements} - H05H 2007/025: {Radiofrequency systems} - H05H: PLASMA TECHNIQUE (apparatus or processes specially adapted for producing X-rays H05G2/00); PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract A method of operating an acceleration system comprises injecting charged particles into an RF accelerator, providing RF power to the accelerator, and accelerating the injected charged particles. The accelerated charged particles may impact a target to generate radiation. The RF power is based, at least in part, on past performance of the system, to compensate, at least partially, for dose and/or energy instability. A controller may provide a compensated control voltage (“CCV”) to an electric power source based on the past performance, to provide compensated electric power to the RF source. A decreasing CCV, such as an exponentially decreasing CCV, may be provided to the electric power source during beam on time periods. The CCV to be provided may be increased, such as exponentially increased toward a maximum value, during beam off time periods. The controller may be configured by a compensation circuit and/or software. Systems are also described. ## Claims ### Claim 1 A stabilized radio-frequency (“RF”) accelerator system, comprising: an RF accelerator to accelerate charged particles; an RF source coupled to the accelerator to provide RF power into the accelerator; a charged particle source coupled to the accelerator to inject charged particles into the accelerator; an electric power source coupled to the RF source and the charged particle source to provide electric power thereto; and a controller to control operation of the electric power source, the controller configured to provide a compensated control voltage to the electric power source; wherein: the electric power provided to the RF source by the electric power source is based, at least in part, on the compensated control voltage; and the compensated control voltage is based, at least in part, on past performance of the system. ### Claim 2 (depends on 1) The system of claim 1, wherein the controller is configured to determine a present compensated control voltage during a beam on time period by: decreasing a prior compensated control voltage from a first value to the present compensation control voltage during a beam on time period; the method further comprising: providing the present compensated control voltage to the electric power source during the beam on time period. ### Claim 3 (depends on 2) The system of claim 2, wherein the controller is further configured to determine a present compensated control voltage during a beam off time period by: increasing a prior compensated control voltage from a first value to the present compensation control voltage; the method further comprising: providing the present compensated control voltage to the electric power source during the beam on time period. ### Claim 4 (depends on 3) The system of claim 3, wherein the controller is configured to determine the present compensated control voltage by: retrieving a nominal control voltage stored by the system; adjusting the retrieved value of the nominal control voltage value by a compensation value, determined by: exponentially decreasing a prior compensation value to the present compensation value during a beam on time period; and/or exponentially increasing the prior compensation value toward a maximum compensation value, to the present compensation value, during a beam off time period. ### Claim 5 (depends on 4) The system of claim 4, wherein the controller is configured to determine the compensation value by a compensation circuit. ### Claim 6 (depends on 5) The system of claim 5, wherein the compensation circuit comprises an R-C circuit comprising: a capacitor; and a resistor; wherein the R-C circuit is configured to allow the capacitor to discharge during the beam on time period, providing exponentially decreasing present compensation values to the electric power source during beam on time periods, based, at least in part, on a respective current voltage of the capacitor during the beam on time period. ### Claim 7 (depends on 6) The system of claim 6, wherein: the compensation circuit further comprises a second R-C circuit comprising: the capacitor; and a second resistor; wherein the second R-C circuit is configured to allow the capacitor to charge exponentially toward a maximum voltage during beam off time periods. ### Claim 8 (depends on 7) The system of claim 7, wherein the compensation circuit further comprises: a diode between the second resistor and the capacitor; an input to provide a reference voltage to charge the capacitor through the second resistor and the diode, during beam off time periods; a first ground, wherein the capacitor discharges to the first ground through the first resistor during beam on time period; an inverting attenuator coupled to the capacitor to invert and attenuate the current voltage of the capacitor during the beam on time period, wherein the present compensation value is an output of the inverting attenuator; and a second ground between the second resistor and the diode, wherein the reference voltage selectively discharges to the second ground through the second resistor during the beam on time period. ### Claim 9 (depends on 8) The system of claim 8, wherein the reference voltage is based, at least in part, on a pulse repetition frequency of a generated beam during the beam on time period. ### Claim 10 (depends on 9) The system of claim 9, further comprising: a first switch to selectively couple the capacitor to the first ground through the first resistor during the beam on time period, to allow the capacitor to discharge to the first ground; and a second switch to selectively couple the second resistor to the second ground during the beam off time period, to allow current in the second resistor to flow to the second ground; wherein the first switch and the second switch are controlled by the controller. ### Claim 11 (depends on 8) The system of claim 8, wherein; the first resistor is a variable resistor; and the second resistor is a variable resistor. ### Claim 12 (depends on 6) The system of claim 6, wherein the RC circuit has a time constant based, at least in part, on the past performance of the system. ### Claim 13 (depends on 12) The system of claim 12, wherein the second R-C circuit has a second time constant based, at least in part, on the past performance of the system to exponentially increase the charge of the capacitor toward a maximum voltage. ### Claim 14 (depends on 12) The system of claim 12, wherein; the first resistor is a variable resistor; the second resistor is a variable resistor; and the first and second time constants are set, at least in part, by setting the resistances of the first and second variable resistors, respectively. ### Claim 15 (depends on 4) The system of claim 4, wherein the controller is configured to determine the present compensation value by software. ### Claim 16 (depends on 15) The system of claim 15, wherein the controller is configured by the software to: periodically adjust a nominal control voltage value by a compensation value, wherein the compensation value is determined by: periodically determining whether the status of system is beam on or beam off; if the determined status is determined to be beam on, exponentially decrease the prior compensation value to a present compensation value by an increment based, at least in part, on a time period and an instability time constant based, at least in part, on past performance of the system; and if the determined status is determined to be beam off, exponentially increase the present compensation value by an increment toward a maximum value, based, at least in part, on a time period and an instability time constant based, at least in part, on the past performance of the system. ### Claim 17 (depends on 16) The system of claim 16, wherein the software is configured to cause the controller to: provide a maximum compensation value at a start of a first beam on period upon a cold start; and determine the present compensation value by exponentially decreasing the maximum compensation value to the present compensation value. ### Claim 18 (depends on 1) The system of claim 1, further comprising: a target material positioned to be impacted by accelerated charged particles. ### Claim 19 A method of operating a charged particle acceleration system, comprising: injecting charged particles into an RF accelerator; providing RF power to the accelerator, the RF power being based, at least in part, on past performance of the system, to compensate, at least in part, for dose and/or energy instability; and accelerating the injected charged particles by the accelerator. ### Claim 20 (depends on 19) The method of claim 19, further comprising: providing compensated electric power to the RF source, the compensated electric power being based, at least in part, on past performance of the system, to compensate, at least in part, for dose and/or energy instability; wherein the RF power provided to the accelerator is based, at least in part, on the compensated electric power. ### Claim 21 A charged particle acceleration system, comprising: accelerator means for accelerating charged particles; means for injecting charged particles into the accelerating means; RF power means for providing RF power to the acceleration means based, at least in part, on past performance of the system, to compensate, at least in part, for dose and/or energy instability; electric power means for providing electric power to the RF power means; and accelerating the injected charged particles by the accelerator means. ### Claim 22 (depends on 21) The system of claim 21, wherein: the electric power means provides electric power to the RF power means based, at least in part, on the past performance of the system; and the RF power provided to the accelerator by the RF power means is based, at least in part, on the electric power provided by the electric power means.