Tong Dechun

A portable X-band on-axis standing wave linac structure

A portable X-band on-axis standing wave electron linear accelerating structure has been developed that is suitable for portable radiation therapy and radiography. The phase-focusing technique is used. The design parameters of a 2 MeV, X-band, on-axis coupled, SW accelerating guide operated in the /spl pi//2 mode is described. A prototype 150 mm long structure has been machined, brazed and sealed, and the experimental data of the cold tests and beam tests are presented.

RF measurements of a C-band cavity beam position monitor*

RF cold test of a novel C-band cavity beam position monitor (PBM) to be used in the SDUVFEL Test Facility is described. The test results are presented and some characteristics discussed. The main parameters obtained are in reasonable agreement with the analytical estimations. Effective suppression of the common mode has been demonstrated. The position sensitivity over the test region of ±0.5 mm is about −21.58 dB/10 μm for the TM110 mode and is linear in the central region of the BPM cavity.

RF gun for an intense THz radiation source

A new facility is under construction at the Shanghai Institute of Applied Physics, to generate femto-second electron bunches and intense coherent THz radiation pulses. A thermionic RF-gun is used to be the electron source of the linac, which is 1.6 cell, π/2, side coupled in design. In the following of this paper, the design, manufacture and beam operation of this gun are presented.

Genetic algorithm diagnosis of individual cell frequencies in a coupled cavity chain

Abstract Genetic algorithms (GAs) are used to diagnose individual cell frequencies in a coupled cavity chain without any perturbing objects. The cell frequencies and couplings between the cells are determined in terms of the measured pass-band performance. The analysis simplifies the tuning processes and enables the tuning of the sealed cavities possible. The problem is solved as an optimization problem with GAs used as a function optimizer. The convergence is improved using the nonlinear least-squares method as a modification of the GAs, which also improves the precision of the solution. The effectiveness of the new technique is demonstrated through some numerical examples and the results are compared with those of the conventional GAs.

Diagnosis of individual cell frequencies in a coupled cavity chain without introducing objects into the cavity

In this paper, a new method that can diagnose the cell frequencies in a cavity without a perturbing probe is presented. The cell frequencies and couplings between cells are estimated in terms of the measured pass-band performance. This method will simplify the tuning processes and make the tuning of a sealed cavity possible. It has been well checked with some numerical examples.

Backward traveling wave electron linac

Future electron linacs will require high gradient acceleration. This paper studies the high shunt impedance backward traveling wave electron linac accelerating structure (BTW). Experiments were performed to prove the feasibility of the BTW structure.

14 MeV single-section SW guide for medical accelerators

A 14 MeV, on-axis coupled, S-band waveguide for medical accelerators was built and tested between 1993 and 1995. The accelerator design, the results of cold and hot tests and the beam performance are given in this paper.

The theory of the harmonically resonant cavity with a self-excited multiple frequency field

Abstract Usually a harmonically resonant cavity is excited by two different wavelength microwave power sources [C.E. Hess, H.A. Schwettman and T.I. Smith, IEEE Trans. Nucl. Sci. NS-32 (1985) 2924]. According to the theory of interaction of the beam with the cavity [P.B. Wilson, AIP Conf. Proc. no. 87 (1982) 450], we found that there is the possibility to excite the harmonically resonant cavity with only the fundamental frequency, and the harmonic frequency electric field will be produced by the beam itself. In this article the formulae for satisfying the condition of the harmonically resonant cavity with self-excited multiple frequency field are given.