RU181147U1 - Synchrocyclotron Automated Proton Beam Moderator - Degrader - Google Patents

Abstract

A useful model is proposed — an automated proton beam moderator of a synchrocyclotron — a degrader operating in the range of 0–1000 MeV. The degrader consists of a set of N pieces of cylindrical absorbers of different lengths and one wedge-shaped absorber made of copper. Absorbers are software installed along the axis of the beam using a computer. The number and lengths of absorber cylinders in the decibal step-by-step scale are chosen so that the sizes of the cylinders are a number series multiple of the ratio 1: 2: 2: 5, and the sum of their lengths is equal to the length of the total absorption of protons in the material of the cylinders. The degrader is designed to work as a set equipment of stands of the Scientific Research Institute of Space Instrument Engineering for testing the reliability of integrated electronic equipment for aerospace purposes.

Description

The proposed utility model relates to accelerator technology and experimental nuclear physics.

The device is designed to change and adjust in a very large energy range of the proton beam of accelerators such as cyclotron, synchrocyclotron.

Note that in the domestic scientific literature there is no established single term for the name of the proposed device. In the state. standard (GOST 22491-87 (ST SEV 5056-85). "Accelerators of charged particles".) [1] - the definition and name of the proposed device is also missing. The names used are: proton beam moderator, proton beam absorber. In English-language literature, the name is adopted - degrader, which is also used in Russian-language literature. In some works, not the entire device as a whole is called a degrader, but only that unit is an absorber, in which proton energy loss occurs directly.

Introduction to the problem. It is known that for a number of scientific research and applied work, proton beams with controlled energy from almost ~ 0 to very high values of ~ 1000 MeV are required. Such proton beams are necessary, for example, for testing and testing the reliability of integrated electronic equipment for aerospace purposes, which, when operating in harsh space conditions, is exposed to atmospheric and cosmic protons in the energy range 0-1000 MeV (A. I. Chumakov. “The effect of space radiation on integrated circuits ”, M.“ Radio and Communications ”, 2004.) [2], (RD 134-0175-2009. Normative document for standardization of the RCT. Radio-electronic equipment for spacecraft. Registered TsKBS FSUE TsNII ashinostroeniya 07.12.2009 for №19780) [3]. For these purposes, only accelerators of the synchrocyclotron type in Dubna for 660 MeV proton energy can be used as generators of protons of such high energies in the Russian Federation (V.M. Abazov, G.A. Andreev, A.N. Bratin et al. “Beams of nucleons and JINR Phasotron Mesons for Physical and Applied Research. ”JINR Preprint 9-90-289, Dubna. 1990) [4] and a synchrocyclotron in Gatchina for an energy of 1000 MeV (NK Abrosimov, GF Mikheev.“ Radio engineering systems of the synchrocyclotron Petersburg Institute of Nuclear Physics ”, Gatchina, 2012) [5]. However, synchrocyclotrons are accelerators of constant proton energy and their operating principle does not allow it to be changed or regulated (J. Livengood. "Principles of operation of cyclic accelerators", M, Publishing House of Foreign Literature, 1963.) [6]. Therefore, to solve the problem, a proton beam moderator is used - a degrader, which allows you to change and adjust the energy of the proton beam already extracted from the accelerator.

The simplest degrader is a plane-parallel block of some material (copper, carbon, water, plastic, etc.), which is installed along the axis of the proton beam already extracted from the accelerator. Protons passing through the block experience inhibition due to the mechanism of ionization and nuclear losses in the substance of the moderator block and exit it with less energy, the value of which depends on the length and material of the block and is determined by calculation or experimentally. The authors are not aware of degraders for the synchrocyclotron, which slow down the proton beam in the range from the synchrocyclotron energy E _max to 0.

In the present application for a utility model, a device is proposed: an automated proton beam moderator of a synchrocyclotron — a degrader that can slow down protons and regulate their energy in the range 1000–0 MeV with an accuracy of ~ 1%.

The 2017 US patent “System for adjusting the energy level of a proton beam provided by a cyclotron, a cyclotron target holder assembly with a removable degrader” was chosen as an analogue. , a removable degrader for use in a cyclotron target holder assembly, and methods of use thereof) [7]. The analog is essentially a proton beam degrador of the PETtrace 880 cyclotron and serves to slow down the beam when irradiating targets for various purposes.

The analog device consists of a proton energy absorber made in the form of a disk of aluminum with a diameter of ~ 30 mm and a thickness of 1 ÷ 0.5 mm. The absorber is fixedly mounted on the holder in one of the three chambers of the cylindrical box. In other boxing chambers are the irradiated target and the collimator. Boxing is mounted in a vacuum path for transporting its proton beam unified with the cyclotron. There are locks and a cassette for changing absorbers without violating the vacuum and a pressure equalization system between the chambers.

The analog device works as follows. The proton beam of a cyclotron with an energy of 16.5 MeV reaches the box and through the collimator it enters the proton energy absorber in the form of an aluminum disk, where due to ionization losses in the absorber material it loses part of its energy (slows down) and leaves the absorber with an energy of ~ 11-12 MeV. Then the beam hits the irradiated target located in another boxing chamber. Depending on the tasks, the energy at the exit of the degrader can be changed by changing the absorbers. Such a change is made "manually" through the gateways with the cassette without violating the vacuum.

The disadvantage of the analog device is the low energy of the proton beam used, a small deceleration range, that is, energy regulation of 1-2%, the lack of automation when adjusting energy, which is carried out by "manual" replacement of the absorbers.

Indeed, in order to slow down protons in a wide range, for example, from 1000 MeV to 0, the thickness of the absorber in the form of a disk (or a set of disks) should be equal to the total absorption length of 1000 MeV protons in aluminum ~ 148 cm. (JF Janni. "Proton range -energy tables, 1 keV - 10 Gev, Atomic data and nuclear data tables ", vol. 27, 1982, pp. 147-529.) [8]. To slow down and adjust the energy of protons, for example, with an interval of 10 MeV, a set of one hundred pieces of individual absorbers — disks — is needed. The design of a degrader of this length is not feasible due to the lack of space in the proton transport path, and replacing such a number of disks in manual mode is not possible due to radiation-hazardous residual radiation of the degrader.

As a prototype, a device designed to slow down and adjust the energies of the extracted proton beam of the JINR synchrocyclotron (Prototype. A.V. Agapov, G.V. Mitsin, K.N. Shipulin. "Automated variable-moderator moderator for proton therapy tasks." JINR , Dubna, R13-2015-97.) [9]. The prototype device consists of a proton energy absorber and a mechanism for moving it. The absorber is made in the form of a wedge of plexiglass. There is a mechanism for its linear auto-movement perpendicular to the axis of the proton beam, there is a stepper motor, a switching unit and an engine power supply, as well as a computer. There is an additional fixed wedge.

The prototype device operates as follows. The main wedge is moved across the axis of the proton beam using a ball screw gear coupled through a clutch with a stepper motor, as a result of which the wedge end can be set at any distance relative to the beam axis, and the proton beam, passing through different paths inside the wedge, is slowed down due to ionization losses and loses part of its energy. The engine through the switch is programmatically controlled by a computer. The degree of proton deceleration is proportional to the thickness of the wedge. The energy adjustment range is ~ 3%. The prototype device, being an automated proton beam moderator of the synchrocyclotron, is essentially a degrader and is designed to change the energy of the extracted proton beam from the JINR synchrocyclotron for radiation exposure of cancer patients, which requires different proton beam energy depending on the type of tumor and its location in the body the patient.

The disadvantage of the prototype device is a very small range of deceleration and regulation of proton energy of ~ 5%, and if necessary, increase it using the circuit of the prototype device, technical difficulties arise.

Indeed, to adjust the proton energy in a wide range, for example, 1000-0 MeV, the size of the base of the wedge, for example, made of copper, should be ~ 53 cm, which is determined by the total absorption length (path length) of protons with an energy of 1000 MeV in the selected substance [ 8]. The height of the wedge should be much larger than its base and be ~ 5 m (the requirement of parallelism of the planes of the wedge), and the mass of the wedge will be ~ 3.5 tons. Naturally, the creation of such a degrader is unrealistic.

The objective of the proposed utility model is to change the design of the degrader by introducing new structural elements and their universal interaction to ensure slowing down of the protons of the synchrocyclotron.

The technical effect consists in creating a real design of a degrader for a synchrocyclotron, which protons are slowed down and their energy is regulated in the entire range from E _max to 0 and with high accuracy.

The technical result is achieved by the fact that in the automated proton beam moderator of a synchrocyclotron a degrader consisting of a proton energy absorber in the form of a wedge and a mechanism for its auto-movement, a new feature is the addition of a set of absorbers made of metal (for example, copper) in the form of cylinders of different lengths installed one after the other along the axis of the proton beam and equipped with a mechanism for their auto-movement across the axis of the beam, the number and length of absorbing cylinders in the decibal scale of the step p gulirovki selected so that the cylinder dimensions were numerical series fold ratio 1: 2: 2: 5, and the sum of their lengths is equal to the length of the total absorption of the protons in the cylinder material.

A utility model diagram is shown in FIG. one.

1. Proton beam absorbers in the form of cylinders (in the amount of N pieces) - cylindrical absorbers.

1A. A proton beam absorber in the form of a wedge-shaped plate is a wedge-shaped absorber.

2. Linear drives for moving absorbers 1, 1A.

3. Holders of absorbers 1, 1A.

4. Clutches of linear drives 2 with stepper motors 5.

5. Stepper motors.

6. The collimator degrader.

7. The casing of the degrader.

In FIG. 2a, b are graphs explaining the operation of the utility model.

The device-degrader consists of a wedge-shaped absorber 1A and a number of cylindrical absorbers 1. Cylindrical absorbers 1 are located one after another as they decrease along the direction of the beam along the OX axis, and the wedge-shaped absorber 1A is located on the exit side of the beam from the degrader. All absorbers are made of metal, such as copper. Linear drives 2 are connected to all absorbers 1 and 1A, each of which consists of a holder 3 for the corresponding absorber 1, 1A, from a screw pair, from a clutch 4 and a stepper motor 5. All stepper motors 5 are connected to a computer through a common communication device. (In Fig. 1 they are not shown). Since the dimensions of the motors 5 do not allow all linear drives 2 to be arranged in the same vertical direction, some of them are offset by an angle α (~ 30 °). The utility model contains a collimator 6 with plug-in bushings to limit the divergence of the proton beam formed by the degrader and is enclosed in a casing 7.

The utility model works as follows. Each of the cylindrical absorbers 1 can be mounted on the axis of the OX proton beam or removed from it using the corresponding linear actuator 2, driven through the clutch 4 by the stepper motor 5. The wedge-shaped absorber 1A is also driven perpendicular to the OX axis and can be installed at any distance from her. In FIG. 1. shows a degrader of eight cylindrical absorbers 1 in a state when one of the absorbers is removed from the OX axis of the proton beam, and the absorber 1A is installed at a certain distance relative to the axis of the OX beam.

The functional purpose of the degrader is step-by-step deceleration and energy regulation of the proton beam with a given step, and to obtain the required energy, the corresponding number of cylindrical absorbers 1 is automatically set along the OX axis and the wedge-shaped absorber 1A is installed at a certain distance from the OX axis. That is, the device we offer is a regulator of direct and discrete (step, step) action.

Let us explain the design features and the principle of operation of the utility model in detail.

In FIG. Figure 2a shows a graph of E (L) - the dependence of the proton beam energy E as it passes through an absorber of length L. The point E _max corresponds to the maximum energy of the synchrocyclotron in the absence of an absorber (L = 0). The point L _max corresponds to the maximum length of the absorber, at which there is complete absorption of proton energy with an energy E _max in the selected material of the absorber. (For example, the mean free path of protons at E _max = 1000 MeV, for copper L _max ≈53 cm, for aluminum L _max ≈148 cm [8].) The real form of the dependence E (L) for copper, calculated by the Monte Carlo method computer modeling using special programs is given, for example, in (S.A. Artamonov, E.M. Ivanov, N.A. Ivanov, Zh.S. Lebedeva, G.A. Ryabov. “Calculation and optimization of proton beams of a variable energy of 60-1000 MeV at the PNPI synchrocyclotron for testing the radiation resistance of electronics. ”Letters in ECHAYA, 2017, vol. 14, No. 1 (206), pp. 144-163.) [10].

,

, …,

для оптимизации конструкции предлагаемого деградера.From FIG. Figure 2a shows that in order to obtain proton energy E _k (point k), it is necessary to install an absorber of length L _k in the degrader, and to obtain energy E _{k + 1} (point k + 1), it is necessary to set the length of the absorber L _{k + 1} . It follows that if it is required to slow down the energy with a step ΔЕ = 10%, then N = 10 absorbers of different lengths are required, and if with a step ΔЕ = 1%, then N = 100 absorbers of different lengths are required, i.e., the number of absorbers N should be equal to the number of steps in energy regulation. We note that the lengths (sizes) of these absorbers are not multiple and are determined by the specific form of the nonlinear dependence E (L). Therefore, a significant problem is the determination of the required minimum number of absorbers N and their sizes

,

, ...,

to optimize the design of the proposed degrader.

цилиндрических поглотителей 1, а добавочная величина L_A устанавливается при помощи клиновидного поглотителя 1А. При этом для изменения энергии протонов, например, в диапазоне 0-1000 МэВ с шагом 100 МэВ требуется не 10, а N=4 цилиндрических поглотителя, а с шагом 10 МэВ требуется не 100, а всего N=8 цилиндрических поглотителя, длины которых

выбираются определенным образом.We will explain in detail. Connect the points E _max and L _{max by a} straight line, the equation of which is E ₁ (L), FIG. 26. It is seen that in order to obtain the proton energy E _k (point k) at the output of the degrader, it is necessary to establish the total length of the absorbers L _K = L ₁ + L _A. In the proposed device, the length L _{1 is} set by the appropriate set

cylindrical absorbers 1, and the additional value L _{A is} set using a wedge-shaped absorber 1A. Moreover, to change the proton energy, for example, in the range of 0-1000 MeV with a step of 100 MeV, not 10, but N = 4 cylindrical absorbers are required, and with a step of 10 MeV, not 100, but only N = 8 cylindrical absorbers are required, the lengths of which

are selected in a certain way.

,

, …,

. Для этого разобьем длину полного поглощения протонов L_max=531.1 мм на 4 отрезка

,

,

,

в отношении 1:2:2:5 и получим размеры 4-х цилиндрических поглотителей:

,

,

,

, где б=0.1L_max=53.11 мм. Легко убедиться, что их сумма

равна 531.1 мм, а их различные сочетания последовательно реализуют 10 величин длины поглотителя

с равным шагом: L₁(1000 МэВ)=0;

;

,

,

,

;

;

;

;

;

. К найденным размерам

цилиндрических поглотителей 1, рассчитанных для 10 точек энергии протонов Е_к, необходимо добавить 10 размеров L_A клиновидного поглотителя 1А, Фиг. 2б. Так как величины L_К известны и приведены, например, в [10], то 10 размеров L_A клиновидного поглотителя 1А находятся как разность L_A=L_K-L₁ для каждого из 10 шагов регулировки энергии.As an example, let us consider the calculation of a degrader for a 1000 MeV synchrocyclotron of PNPI SIC KI [5], when the proton energy slows down from 1000 MeV to 0 with an equal step of 100 MeV and is fixed at 10 points. Find the number N of cylindrical absorbers 1 necessary for this and their sizes

,

, ...,

. For this, we divide the length of the total absorption of protons L _max = 531.1 mm into 4 segments

,

,

,

in the ratio 1: 2: 2: 5 and we get the dimensions of 4 cylindrical absorbers:

,

,

,

where b = 0.1L _max = 53.11 mm. It is easy to verify that their sum

is equal to 531.1 mm, and their various combinations sequentially realize 10 values of the length of the absorber

with an equal step: L ₁ (1000 MeV) = 0;

;

,

,

,

;

;

;

;

;

. To found sizes

cylindrical absorbers 1, calculated for 10 points of proton energy E _to , you must add 10 sizes L _A wedge-shaped absorber 1A, Fig. 2b. Since the values of L _{K are} known and are given, for example, in [10], then 10 sizes L _{A of the} wedge-shaped absorber 1A are found as the difference L _A = L _K -L ₁ for each of the 10 steps of energy regulation.

Thus, to slow down the proton energy in increments of ΔE = 100 MeV (10%), it is sufficient to have N = 4 cylindrical absorbers 1 and one wedge-shaped 1A.

,

,

,

,

,

,

,

, где б=5.311 мм. Легко убедиться, что их сумма

равна длине полного поглощения протонов с энергией 1000 МэВ в меди 531.11 мм, а их различные сочетания последовательно реализуют 100 различных длин поглотителей L₁ с равным шагом ΔL₁=б=5.311 мм.The lengths of all absorbers are calculated in a similar way when the proton energy slows down from 1000 MeV to 0 with an equal step of 10 MeV and is fixed at 100 points. In this case, the dimensions of the cylindrical 8 absorbers are determined in the form of a series of numbers that are multiples of 1: 2: 2: 5 and will be:

,

,

,

,

,

,

,

where b = 5.311 mm. It is easy to verify that their sum

equal to the total absorption length of protons with an energy of 1000 MeV in copper 531.11 mm, and their various combinations sequentially realize 100 different lengths of absorbers L ₁ with equal pitch ΔL ₁ = b = 5.311 mm.

Thus, to slow down and adjust the proton energy with a step ΔE = 10 MeV (1%), it is sufficient to have not 100, but only 8 pieces of cylindrical absorbers 1 and one wedge-shaped 1A.

,

, …,

должны составлять числовой ряд кратный соотношению 1:2:2:5.In the general case, when the degrader is operating in the decibal adjustment scale, when the number of steps to cover the entire energy range 0 - E _{max is} selected as a multiple of 10, the sizes of the absorbing cylinders are selected as follows. The total length of all N cylinders should be equal to the length of the total absorption of protons L _max , and the length of individual cylinders

,

, ...,

must be a number series multiple of the ratio 1: 2: 2: 5.

,

,

,

,

,

,

,

. При этом б=0.01 L_max - является шагом регулировки и равна длине наименьшего из цилиндров

. (Отметим, что соотношение 1:2:2:5 хорошо известно из числовой информатики, в частности, оно применяется для минимизации набора гирь-разновесов для взвешивания тел на одночашечных весах (ГОСТ7328-82) [11]).For example, for 100 steps of energy regulation, a set of absorbers should contain N = 8 cylinders, the dimensions of which will be:

,

,

,

,

,

,

,

. Moreover, b = 0.01 L _max - is the adjustment step and is equal to the length of the smallest of cylinders

. (Note that the ratio 1: 2: 2: 5 is well known from numerical informatics, in particular, it is used to minimize the set of weights-weights for weighing bodies on single-cup scales (GOST 7328-82) [11]).

Thus, with an increase in the number of energy adjustment steps (required for the degrader to work), the advantage of the proposed utility model is revealed, which consists in a sharp decrease in the number N, that is, the number of necessary structural elements of the device.

We also note that in the proposed model of a degrader, the possibility of adjusting the energy in 1% increments even exceeds the accuracy of measuring proton energy, for example, by the “time of flight” method, and also exceeds the inhomogeneity of the energy of the proton beam of the synchrocyclotron, which is ~ 1-3%.

It is important to note that the inclusion in the design of the proposed device of a joint set of wedge-shaped absorber 1A and cylindrical absorbers 1 is not the sum of borrowings from the analogue [7] and prototype [9], but is fundamentally and significantly different due to their different functional purpose. Indeed, the wedge-shaped absorber fulfills the function of linearizing the dependence E (L) and, therefore, minimizes the number N, the number of cylindrical absorbers needed to adjust the energy with a given step.

Thus, the main positive differences between the proposed utility model and the prototype device and all known analogues are the ability to slow down protons and adjust the energy of the extracted proton beam of the synchrocyclotron in a very large range with high accuracy, as well as the ability to quickly automatically reconfigure the energy of the proton beam (which is very important with serial express radiation of electronics). Moreover, the design of the utility model is simple and compact.

The utility model of the degrader was tested at the 1000 MeV synchrocyclotron of PNPI SIC KI. The main parameters of the degrader model:

The absorber material is copper, density 8.88 g / cm ³ . The number of main absorbers N = 8 pcs., Diameter 80 mm. The dimensions of the wedge-shaped absorber are 250 cm high, 80 mm wide, and 6 cm wedge thickness. The holders are made of aluminum. Linear drives are standard mechanisms. The dimensions of the degrader casing are 0.4 × 0.7 × 1.0 m ³ . The weight of the degrader is 25 kg.

The degrader is designed to work in a set of equipment of the stands of the Research Institute of Space Instrument Engineering for testing the reliability of integrated electronic radio equipment for aerospace purposes.

Literature

1. GOST 22491-87 (ST SEV 5056-85). "Accelerators of charged particles."

2. A.I. Chumakov.

“The effect of cosmic radiation on integrated circuits”, M. “Radio and communications”, 2004.

3. RD 134-0175-2009. Normative document for standardization of RCT. On-board radio-electronic equipment for spacecraft (registered by TsKBS FSUE Central Research Institute of Mechanical Engineering on December 7, 2009, No. 19780).

4. V.M. Abazov, G.A. Andreev, A.N. Brother et al.

"Junction beams of nucleons and mesons of the JINR phasotron for physical and applied research." JINR Preprint 9-90-289, Dubna. 1990.

5. N.K. Abrosimov, G.F. Mikheev.

“Radio engineering systems of the synchrocyclotron of the St. Petersburg Institute of Nuclear Physics”, Gatchina, 2012.

6. J. Livengood.

"The principles of operation of cyclic accelerators", M, Publishing house of Inostr. lit., 1963.

7. Analog.

United States Patent 9789341.

"System for adjusting the energy level of a proton beam provided by a cyclotron, a cyclotron target holder assembly with a removable degrader, a removable degrader for use in a cyclotron target holder assembly, and methods of use thereof.

8. J.F. Jarnni.

"Proton range-energy tables, 1keV - 10Gev, Atomic data and nuclear data tables", vol. 27, 1982, pp. 147-529.

9. The prototype.

A.B. Agapov, G.V. Mitsin, K.H. Shipulin.

"An automated retarder of variable thickness for proton therapy applications." JINR, Dubna, R13-2015-97.

10. S.A. Artamonov, E.M. Ivanovna. Ivanov, J.S. Lebedeva, G.A. Ryabov.

"Calculation and optimization of proton beams of variable energy 60-1000 MeV at the PNPI synchrocyclotron for testing the radiation resistance of electronics." Letters to ECHAYA, 2017, v. 14, No. 1 (206), p. 144-163.

11. GOST 7328-82.

Claims (1)

An automated proton beam moderator of a synchrocyclotron is a degrader, consisting of a proton energy absorber in the form of a wedge and a mechanism for its auto-movement, characterized in that a set of metal absorbers (for example, copper) in the form of cylinders of different lengths, installed one after the other along the axis of the proton beam, is additionally introduced and equipped with a mechanism for their auto-movement across the axis of the beam, and the number and length of the absorber cylinders in the decibal scale of step adjustment is chosen so that the dimensions of the cylinder s numerical series made multiple ratio 1: 2: 2: 5, and the sum of their lengths is equal to the length of the total absorption of the protons in the cylinder material.

Images