Device and method for regulating intensity of beam extracted from a particle accelerator

• US 6,873,123 B2
• Filed: 06/03/2002
• Issued: 03/29/2005
• Est. Priority Date: 06/08/2001
• Status: Expired due to Fees

• Current Assignee: Ion Beam Applications s.a.
• Original Assignee: Ion Beam Applications s.a.
• Inventors: Bauvir, Bertrand, Marchand, Bruno
• Primary Examiner(s): Wells, Nikita
• Application Number:
  US10/479,380
• Publication Number:
  US 20040155206A1
• Time in Patent Office: 1,030 Days
• Field of Search: 315/502, 315/507, 315/111.61, 315/111.81, 250/505.1, 250/423.R, 250/424, 250/492.3, 250/492.1, 250/396.R
• US Class Current: 315/502
• CPC Class Codes: H05H 13/00 Magnetic resonance accelerators; Cyclotrons strophotrons, turbine tubes H01J25/62
• CPC Class Codes: H05H 7/00 Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00

Abstract

The invention concerns a device (10) for regulating the intensity of a beam extracted from a particle accelerator, such as a cyclotron, used for example for protontherapy, said particles being generated from an ion source. The invention is characterized in that it comprises at least: a comparator (90) determining a difference ε between a digital signal I_R representing the intensity of the beam measured at the output of the accelerator and a setpoint value I_C of the beam intensity: a Smith predictor (80) which determines on the basis of the difference ε, a correct value of the intensity of the beam I_P; an inverted correspondence table (40) supplying, on the basis of the corrected value of the intensity of the beam I_P, a setpoint value I_A for supply arc current from the ion source (20).

Claims

1. A device (10) for regulating the intensity of the beam extracted from a particle accelerator, such as a cyclotron, used for example for proton therapy, said particles being generated from an ion source, characterized in that it includes at least:

a comparator (90), which determines a difference ε

between a digital signal I_R representative of the beam intensity measured at the output of the accelerator and a setpoint value of the beam intensity I_C;

a Smith predictor (80), which determines a corrected value of the beam intensity I_P on the basis of the difference ε

;

an inverted correspondence table (40), which provides a setpoint value I_A for the supply of the arc current of the ion source (20) on the basis of the corrected value of the beam intensity I_P.

2. The device as claimed in claim 1, characterized in that it furthermore comprises an analog-digital converter (50), which converts the analog signal I_M directly representative of the beam intensity measured at the output of the accelerator and provides a digital signal I_R.

3. The device as claimed in claim 1, characterized in that it furthermore comprises:

a lowpass filter (60), which filters the analog signal I_M directly representative of the beam intensity measured at the output of the accelerator and provides a filtered analog signal I_F;

a phase lead controller (70), which samples the filtered analog signal I^F, compensates for the phase lag introduced by the lowpass filter (60) and provides a digital signal I_R to the comparator (90).

4. The device as claimed in claim 1, characterized in that it includes means for updating the content of the inverted correspondence table (40).

5. The device as claimed in claim 1, characterized in that the sampling frequency is between 100 kHz and 200 kHz.

6. The device as claimed in claim 1, characterized in that the cutoff frequency of the lowpass filter (60) is between 2 and 6 kHz.

7. Use of the device as claimed in claim 1 in proton therapy, and in particular in the techniques of “

Pencil Beam Scanning” and

“

double scattering”

.

13. Use of the method of as claimed in claim 7 in proton therapy, and in particular in the techniques of “

Pencil Beam Scanning” and

“

double scattering”

.

8. A method for regulating the intensity of the beam extracted from a particle accelerator, such as a cyclotron, used for example for proton therapy, said particles being generated from an ion source (20), by means of a digital regulation device (10) operating at a given sampling frequency, characterized in that it comprises at least the following stages:

the beam intensity (I_M) is measured at the output of the particle accelerator;

a digital signal I_R representative of the measurement of the beam intensity (I_M) is compared with the setpoint value I_C of the beam intensity, by means of a comparator (90);

a corrected value of the beam intensity I_P is determined by means of a Smith predictor (80);

a setpoint value I_A for the supply of the arc current of the ion source (20) is determined, on the basis of the corrected value I_P of the beam intensity, by means of an inverted correspondence table (40).

9. The regulation method as claimed in claim 8, characterized in that, after the measurement of the beam intensity at the output of the particle accelerator, the analog signal I_M directly representative of the measured beam intensity is converted by means of an analog-digital converter (50) in order to obtain a digital signal I_R.

10. The method as claimed in claim 8, characterized in that after the measurement of the beam intensity at the output of the particle accelerator:

the analog signal I_M directly representative of the measured beam intensity is filtered by means of a lowpass filter (60), giving a filtered analog signal I_F;

the filtered analog signal I_F is sampled, and the phase lag introduced by the filtering is compensated with the aid of a phase lead controller (70), in order to obtain a digital signal I_R.

11. The method as claimed in claim 8, characterized in that the correspondence between a value I_A for the supply of the arc current of the ion source (20) and a value I_M of the beam intensity measured at the output of the accelerator is determined prior to the regulation.

12. The method as claimed in claim 8, characterized in that, in the correspondence between a value I_M of the beam intensity measured at the output of the accelerator and a value I_A for the supply of the arc current of the ion source, the values of I_A corresponding to the values of I_M higher than a limit are replaced by the value of I_A corresponding to this limit.