Study on the radiation problem caused by electron beam loss in accelerator tubes

The beam dynamic code PARMELA was used to simulate the transportation process of accelerating electrons in S-band SW linacs with different energies of 2.5, 6 and 20 MeV. The results indicated that in the ideal condition, the percentage of electron beam loss was 50% in accelerator tubes. Also we calculated the spectrum, the location and angular distribution of the lost electrons. Calculation performed by Monte Carlo code MCNP demonstrated that the radiation distribution of lost electrons was nearly uniform along the tube axis, the angular distributions of the radiation dose rates of the three tubes were similar, and the highest leaking dose was at the angle of 160° with respect to the axis. The lower the energy of the accelerator, the higher the radiation relative leakage. For the 2.5 MeV accelerator, the maximum dose rate reached 5% of the main dose and the one on the head of the electron gun was 1%, both of which did not meet the eligible protection requirement for accelerators. We adopted different shielding designs for different accelerators. The simulated result showed that the shielded radiation leaking dose rates fulfilled the requirement.

Physical design and cooling test of C-band standing wave accelerating tube

The physical design and cooling test of a C-band 2MeV standing wave （SW） accelerating tube are described in this paper. The designed accelerating structure consists of 3-cell buncher and 4-cell accelerating section with a total length of about 163mm, excited with 1MW magnetron. Dynamic simulation presents that about 150mA beam pulse current and 30% capture efficiency can be achieved. By means of nonlinear Gauss fit on electron transverse distribution, the diameter of beam spot FWHM （full width at half maximum of density distribution） is about 0.55mm. Cooling test results of the accelerating tube show that frequencies of cavities are tuned to 5527MHz and the field distribution of bunching section is about 3：9：10.

Experimental research on the feature of an x-ray Talbot–Lau interferometer versus tube accelerating voltage

X-ray Talbot-Lau interferometer has been used most widely to perform x-ray phase-contrast imaging with a con- ventional low-brilliance x-ray source, and it yields high-sensitivity phase and dark-field images of samples producing low absorption contrast, thus beating tremendous potential for future clinical diagnosis. In this work, by changing the accel- erating voltage of the x-ray tube from 35 kV to 45 kV, x-ray phase-contrast imaging of a test sample is performed at each integer value of the accelerating voltage to investigate the characteristic of an x-ray Talbot-Lau interferometer （located in the Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Japan） versus tube voltage. Ex- perimental results and data analysis show that within a range this x-ray Talbot-Lau interferometer is not sensitive to the accelerating voltage of the tube with a constant fringe visibility of ~ 44%. This x-ray Talbot-Lau interferometer research demonstrates the feasibility of a new dual energy phase-contrast x-ray imaging strategy and the possibility to collect a refraction spectrum.

Beam dynamics design for uranium drift tube linear accelerator

KONUS beam dynamics design of uranium whose current is 5.0 emA, is accelerated from injection DTL with LORASR code is presented. The 238U34＋ beam, energy of 0.35 MeV/u to output energy of 1.30 MeV/u by IH-DTL operated at 81.25 MHz in HIAF project at IMP of CAS. It achieves a transmission efficiency of 94.95% with a cavity length of 267.8 cm. The optimization aims are the reduction of emittance growth, beam loss and project costs. Because of the requirements of CW mode operation, the designed average acceleration gradient is about 2.48 MV/m. The maximum axial field is 10.2 MV/m, meanwhile the Kilpatrick breakdown field is 10.56 MV/m at 81.25 MHz.

Microwave Cold Test Debug of an S-Band 2MeV on-Axis Coupling SW Accelerator

This paper presents the model cavity tune and cold test of an S-band 2MeV on-axis coupling SW accelerator. The measurement of the model cavity's frequency,degree of coupling,Q value and on-axis field distribution are described in detail.In addition,the results of cavity tune and cold test of the accelerating tube are given.The frequency consistency of the accelerator is within±0.3MHz,the coupling degree in the supersaturation state 1.14,the quality factor of the accelerator 12000±200,and the field distribution ratio 1:2.2:2.All the results observed show that the accelerator satisfies the physics design with microwave debugging.

Design and Commissioning of a 150MeV Linac for SSRF

A 150MeV injector electron linac for the SSRF is under construction at SINAP.This linac has been installed, commissioned and handed over to the SSRF during the period of 2006—2007.This paper describes the special needs of an injector for a third generation synchrotron light source and the two specific modes of operation for this linac.The design results and the commissioning results for this linac are given in this paper.