Free Electron Laser Monitoring System
Development and Manufacture of the Automatic System of Radiation Monitoring for the High-Power Free Electron Laser
Tech Area / Field
- PHY-PFA/Particles, Fields and Accelerator Physics/Physics
- INS-DET/Detection Devices/Instrumentation
3 Approved without Funding
Budker Institute of Nuclear Physics, Russia, Novosibirsk reg., Akademgorodok
- VNIITF, Russia, Chelyabinsk reg., Snezhinsk
- University of Chicago / Enrico Fermi Institute, USA, IL, Chicago\nKorea Atomic Energy Research Institute, Korea, Yusung Taejon\nBrookhaven National Laboratory, USA, NY, Upton
Project summaryA free electron laser (FEL) with smoothly tuned lasing wavelength seems to be an attractive source of high-intensity coherent radiation for scientific, medical investigations and for technological applications [1, 2]. Over as long as thirty years Budker Institute of Nuclear Physics (BINP) is an acknowledged leader in the field of FEL design and manufacture. At present BINP and Korea Atomic Energy Research Institute (KAERI) are building a high-power infrared FEL (the radiation wavelength is 2 to 20 mm, the average power is up to 100 kW) on the base of cw racetrack microtron-recuperator with electron energy up to 100 MeV and beam current up to 50 mA . Thus, at the maximum energy in the lasing area the power of an electron beam can reach up to 5 MW.
One of the advantages of FEL Project is the potential possibility of significant reduction of the induced radioactivity level in the regular operation mode, because of the use of recuperation of the energy of relativistic electrons. Application of this method allows to limit the radiation protection requirements. However, the operation of the accelerator with such parameters can only be performed with a high level of beam hygiene, which requires, in particular, sufficiently developed diagnostics. Otherwise, a loss of even a small part of the full electron beam leads to the deterioration of the radiation situation, thermal destruction of the vacuum chamber, reduction of lifetime of the non-persistent-to-radiation components of the acceleration equipment.
Generally speaking, a loss of a significant part of the full beam with an electron energy close to the maximum on the walls of the microtron vacuum chamber can not last for any long period for the disturbance of the recuperation, and the RF system is not able to maintain the whole-scale acceleration process. Nevertheless, the level of the permissible losses (if no special measures have been taken to reduce them) can be such that the above-mentioned consequences can become real.
At present neither BINP nor any other organizations in world have any experience of operations with such facilities. At this stage it seems to be necessary to design and manufacture an automatic system of radiation monitoring for the facility under construction (high-power FEL). The system will allow to identify rather rapidly the growth of losses and to stop the acceleration, if necessary. It would be very desirable to attach to the system the diagnostic functions, allowing even approximate determination of the loss location. Combination of these and other requirements put to the functional characteristics of the ASRM for FEL facility under construction make this system a unique one. The monitoring system based on the detection dosimetric units seems reasonable version because of their high sensitivity and simultaneous availability of timely processing, visualization and storage of the information of the radiation situation in FEL facility. In addition, BINP has already obtained experience in designing of automatic systems of radiation monitoring .
Design and manufacture of the automatic system of radiation monitoring for the high-power FEL are the main tasks of this Project and pursue the following aims:
1. Prevention of accident destruction of the microtron-recuperator vacuum chamber by the high-power beam of accelerated electrons because of its insufficient focusing or because of orbit distortion.
2. Radiation safety of the staff.
3. Optimum spending of radiation resource of the least non-persistent-to-radiation components of the equipment (electronic components, polymer material insulation, glass details etc.)
4. Accumulation of data which can be used in the design and/or operation of similar radiation-hazardous units or facilities.
5. Provision of the possibility to predict radiation situation in different operation modes of FEL facility operation and to plan repair-maintenance and other procedures.
6. More efficient control over the quality of facility operation.
Design of the proposed system is determined by the space-time characteristics of the microtron-recuperator radiation fields. These characteristics in turn depend on the space-time distribution of the electron losses from the beam during its beam acceleration, operation utilization in FEL, consequent deceleration and absorption in the dump. The distribution of the beam losses in the acceleration facility known, the radiation fields can be predicted. When pilot operation of the ASRM starts, a possibility appears to define more exactly the characteristics of the radiation fields and beam loss distribution. Promptly obtained information on radiation levels and doses in a appropriate number of control points as well as adequate use of the data obtained will facilitate the achievement of the above-mentioned aims and realization of the high-power FEL project as a whole.
A significant contribution to the designing and development of FEL ASRM component base can be done by the RFNC-VNIITF, possessing the necessary mathematical programs and experimental base. The work on the Project will use mathematical programs PRISMA [5-6], SINARA  and PM2D  made at RFNC-VNIITF as well as betatron BIM-234 with electron energy of up to 70 MeV  and GAMMATOK-100, using gamma radiation of isotope 60Co.
Program complex PRISMA is intended for solving three-dimensional problems of joint transfer of neutrons, photons and charged particles in a substance with the help of the Monte Carlo method. This program complex was widely used at VNIITF for computation of the bremsstrahlung fields of pulsed electron accelerators, of the n-g fields of pulsed reactors, biological shielding against penetrating radiation sources as well as of characteristics of the detectors used to record penetrating radiation. Program PRISMA will be used for detailed computations of spatial distribution, spectral composition and intensity of the secondary radiation because of possible electron losses on the walls of the microtron-recuperator vacuum chamber. Program PRISMA will be used as well for computation of the radiation situation at the dump and behind the biological shield.
To estimate the permissible electron beam losses on walls of the vacuum chamber and the time required for deenergizing the accelerator in case of emergency, two-dimensional gas dynamics computations will be made on the base of the SINARA program .
RFNC-VNIITF with ISTC support on Projects 107 and 767 has developed methods and programs which allow the calculation of three-dimensional trajectories of relativistic electrons in specified electric and magnetic fields. New programs allowing simulation of dynamics of electrons in the recuperator and calculation of permissible beam losses will be created on the base of these programs and PM2D .
The radiation resource of dielectric structural materials (polymer insulation, glass details etc.) will be investigated at RFNC-VNIITF on the GAMMATOK-100 (a Co60 isotope source, the exposure dose rate is up to 106 R/h, the volume of the operation chamber is 40 dm3). This installation will be used also for checking the radiation resistance of the detectors and detecting units.
Calibration of the radiation detectors used for monitoring the radiation situation in the acceleration hall, development and measurement of parameters of the fast emergency detectors as well as the measurement of g-radiation passing through the model assemblies for testing the computations will be performed with the use of bremsstrahlung of betatron BIM-234 with maximum energy of 70 MeV .
1. Proceedings of third Asian symposium on free electron laser and fifth symposium on FEL applications. FELI, Hirakata, Osaka, Japan, 1997.
2. Free electron Laser challenges. Proceedings of SPIE, San Jose, California, 1997.
3. Status of the Novosibirsk high power free electron laser project. Gavrilov N.G. Proceedings of SPIE. Vol. 2988 p.185, 1997.
4. Koryabkin O.M., Repkov A.V., Chudaev V.Ya., Automatic system of radiation monitoring at INP SB AS USSR. // Proceedings of the XII All-Union meeting on charged particle accelerators, Dubna, 1990. – Dubna, 1992. – V. 2. – p.317-320.
5. Kandiev Ya.Z., Plokhoi V.V. Problems of atomic science and technology (PACT), ser. Mathematical modeling of physical processes, iss.2, p.70, 1993.
6. V.V. Plokhoi, Ya. Z. Kandiev IET, v.40, No.5, (1997) pp.25-28.
7. Gadzhiev A.D., GadzhievaV.V., Kuzmin S.Yu., Lebedev C.N., Lebedeva T.V., Pisarev V.N., Romanova E.M., Rykovanova V.V., Sozinov E.A., Shestakov A.A. Program package SINARA for mathematical modeling of emergency process dynamics in nuclear energy plants of atomic electric stations by high-energy neutrons. Preprint of the Russian Federal Nuclear Center – VNIITF No. 129, 1998.
8. I.A.Litvinenko and V.A.Lykov. "The PM-2D code simulation of electromagnetic fields generation at the ultra-short laser pulse interaction with matter." The 13th International Conference Li&RPP. AIP Conference proceedings 406. Editors: G.H.Miley and E.M. Campbell. pp.470-476, 1997.
9. Averyaskin S.N., Anitchenko G.Ya, Nikitin O.A., Popov V.I., Povyshev V.N., Sanin I.V. Report on the XXI International congress on rapid-action photography and photonics, Tajon, Korea, (1994).
Works on the proposed Project are referred to applied investigations in physics of fundamental particles, fields and accelerators.
The main task of the Project is development of the automatic system of radiation monitoring (ASRM) allowing to overcome the difficulties in the normal operation of FEL in the course of commission, adjustment and operation.
It is assumed to obtain some important results during the design the ASRM and its pilot operation in FEL stand:
- Estimates of the distribution of electron beam losses and the microtron-recuperator radiation fields.
- Analysis of the factors effecting lifetime of the devices and the personnel safety.
- Requirements to limitations of radiation loads.
- Possibilities of application of detectors of different types on account of determining the location of the electron beam losses.
The results obtained will be a base for the development of the ASRM general structure and configuration as well as for design and manufacture of the prototypes of:
- the detection units on the base of the detectors selected;
- the protecting and (may be) collimating components (modules) for the detectors;
- the matching devices;
- the ASRM software, which, in particular, is to provide the exchange of necessary data between the ASRM and FEL control system.
After laboratory test of the prototypes of the ASRM components at a special stand and possible improvement of them, the ASRM components will be manufactured and subjected to tests at the same stand. After preparatory works and installation of the ASRM hardware and software the system will be subjected to a complex test under operation conditions.
The Project will be performed in collaboration of BINP and KAERI. The far infrared FEL (FIR FEL) on the base of the 8 MeV microtron and the 2 MeV electron injector for a racetrack microtron-recuperator have already been designed, delivered and commissioned at KAERI in the frame of this collaboration.
The project implies the development the automatic system of radiation monitoring for the high-power FEL under construction at KAERI. This will facilitate commissining and operation of FEL as well as further strengthening of the Russia–Korea collaboration. Besides that, the realization of the Project may promote the generation of ideas for the development of similar systems, provisions for estimation of the heat and radiation loads and recommendations on radiation protection that can be used for other similar projects or accelerators.
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