IPAC2011 - List of Authors (Lau, W.K.)

Paper	Title	Page
MOPC059	The Plane Wave Transformer Linac Development at NSRRC	217
	A. Sadeghipanah, J.-Y. Hwang, W.K. Lau NSRRC, Hsinchu, Taiwan T.H. Chang NTHU, Hsinchu, Taiwan
	A Plane-Wave-Transformer (PWT), standing wave linac operating at S-band frequency (2.9979 GHz) is being developed at NSRRC. This structure offers the advantages of high efficiency, compactness, fabrication simplicity and cost. The PWT prototype at NSRRC consists of three cells with two half-cells at the ends, separated by a set of four flat disks suspended and cooled by four water tubes inside a large cylindrical tank. To fully understand its physical properties, numerical modeling of the PWT prototype has been carried out by using the 2-D code SUPERFISH and 3-D code MAFIA. In this paper, we describe the principle properties of this structure, the electric parameters obtained from numerical simulations, and heat dissipation calculation. The mechanical design for prototype linac is also reported.

TUPC038	A Low Energy Thermionic RF Gun Linac for Ultrashort Electron Beam	1081
	J.-Y. Hwang, J.H. Chen, W.K. Lau, A.P. Lee, T.H. Wu NSRRC, Hsinchu, Taiwan N.Y. Huang NTHU, Hsinchu, Taiwan
	A low energy test linac is being constructed at NSRRC for technological development of high brightness electron injector. It is a 29 MeV S-band linac that equipped with a high gradient thermionic cathode rf gun for generation of ultrashort relativistic electron beam by velocity bunching in the rf linac section located at downstream. High quality GHz-repetition-rate electron pulses of about 30 pC in bunch charge, pulse duration as short as 100 fsec can be produced from this test facility. It can be used as the driver for future light source experiments such as ultrafast head-on inverse Compton scattering (ICS) X-ray source and intense coherent THz free electron lasers.

WEPC036	Coherent Synchrotron Radiation Source Based on an Isochronous Accumulator Ring with Femtosecond Electron Bunches	2085
	N.Y. Huang NTHU, Hsinchu, Taiwan H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, F. Miyahara, T. Muto, K. Nanbu, Y. Tanaka Tohoku University, Research Center for Electron Photon Science, Sendai, Japan W.K. Lau NSRRC, Hsinchu, Taiwan
	A compact isochronous accumulator ring has been studied as a source of coherent synchrotron radiation (CSR) at a wavelength region from THz to GHz. Since the thermionic rf gun is substantially stable in general, we anticipate a bunch train of very short electron pulses can be provided satisfactorily by means of velocity bunching. Careful numerical simulations show possibility of the bunch length of much less than 100 fs with a bunch charge of 20 pC, which will contain sufficiently large form factor for production of CSR at the wavelengths longer than ~ 0.1 mm. The coherent THz radiation of high average power will be achieved if the short bunches can be circulated in the accumulator ring without bunch lengthening. This paper will describe the optimization of thermionic injector to produce femtosecond bunches in addition to study of the lattice designing of complete isochronous optics for the accumulator ring.

THPC066	A Study of Emittance Growth in a Photoinjector Linac by using PWT as Pre-accelerator	3044
	A. Sadeghipanah, S.B. Hung, W.K. Lau, A.P. Lee NSRRC, Hsinchu, Taiwan N.Y. Huang NTHU, Hsinchu, Taiwan
	The NSRRC high brightness photoinjector for light source R&D is a 2998 MHz split configuration. Our goal is to produce 1 nC bunch charge from a photo-cathode rf gun with normalized emittance of 1 mm-mrad or less. However, limited by the available power from our klystron, previous studies showed that our linac has to be equipped with focusing solenoid to help emittance control during acceleration. In order to omit the bulky focusing solenoid from the booster linac system, we considered to use two high gradient (~26 MV/m) PWT standing-wave structures to accelerate the beam previous to the linac. Studies showed that this configuration can keep the emittance as low as 1 mm-mrad while also decreasing the energy spread to half of its initial amount. The only drawback is the growth of final beam radius, which can be compensated by using a setting of quadrupole magnets.

Paper

Title

Page

The Plane Wave Transformer Linac Development at NSRRC

217

A. Sadeghipanah, J.-Y. Hwang, W.K. Lau
NSRRC, Hsinchu, Taiwan
T.H. Chang
NTHU, Hsinchu, Taiwan

A Plane-Wave-Transformer (PWT), standing wave linac operating at S-band frequency (2.9979 GHz) is being developed at NSRRC. This structure offers the advantages of high efficiency, compactness, fabrication simplicity and cost. The PWT prototype at NSRRC consists of three cells with two half-cells at the ends, separated by a set of four flat disks suspended and cooled by four water tubes inside a large cylindrical tank. To fully understand its physical properties, numerical modeling of the PWT prototype has been carried out by using the 2-D code SUPERFISH and 3-D code MAFIA. In this paper, we describe the principle properties of this structure, the electric parameters obtained from numerical simulations, and heat dissipation calculation. The mechanical design for prototype linac is also reported.

TUPC038

A Low Energy Thermionic RF Gun Linac for Ultrashort Electron Beam

1081

J.-Y. Hwang, J.H. Chen, W.K. Lau, A.P. Lee, T.H. Wu
NSRRC, Hsinchu, Taiwan
N.Y. Huang
NTHU, Hsinchu, Taiwan

A low energy test linac is being constructed at NSRRC for technological development of high brightness electron injector. It is a 29 MeV S-band linac that equipped with a high gradient thermionic cathode rf gun for generation of ultrashort relativistic electron beam by velocity bunching in the rf linac section located at downstream. High quality GHz-repetition-rate electron pulses of about 30 pC in bunch charge, pulse duration as short as 100 fsec can be produced from this test facility. It can be used as the driver for future light source experiments such as ultrafast head-on inverse Compton scattering (ICS) X-ray source and intense coherent THz free electron lasers.

WEPC036

Coherent Synchrotron Radiation Source Based on an Isochronous Accumulator Ring with Femtosecond Electron Bunches

2085

N.Y. Huang
NTHU, Hsinchu, Taiwan
H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, F. Miyahara, T. Muto, K. Nanbu, Y. Tanaka
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
W.K. Lau
NSRRC, Hsinchu, Taiwan

A compact isochronous accumulator ring has been studied as a source of coherent synchrotron radiation (CSR) at a wavelength region from THz to GHz. Since the thermionic rf gun is substantially stable in general, we anticipate a bunch train of very short electron pulses can be provided satisfactorily by means of velocity bunching. Careful numerical simulations show possibility of the bunch length of much less than 100 fs with a bunch charge of 20 pC, which will contain sufficiently large form factor for production of CSR at the wavelengths longer than ~ 0.1 mm. The coherent THz radiation of high average power will be achieved if the short bunches can be circulated in the accumulator ring without bunch lengthening. This paper will describe the optimization of thermionic injector to produce femtosecond bunches in addition to study of the lattice designing of complete isochronous optics for the accumulator ring.

THPC066

A Study of Emittance Growth in a Photoinjector Linac by using PWT as Pre-accelerator

3044

A. Sadeghipanah, S.B. Hung, W.K. Lau, A.P. Lee
NSRRC, Hsinchu, Taiwan
N.Y. Huang
NTHU, Hsinchu, Taiwan

The NSRRC high brightness photoinjector for light source R&D is a 2998 MHz split configuration. Our goal is to produce 1 nC bunch charge from a photo-cathode rf gun with normalized emittance of 1 mm-mrad or less. However, limited by the available power from our klystron, previous studies showed that our linac has to be equipped with focusing solenoid to help emittance control during acceleration. In order to omit the bulky focusing solenoid from the booster linac system, we considered to use two high gradient (~26 MV/m) PWT standing-wave structures to accelerate the beam previous to the linac. Studies showed that this configuration can keep the emittance as low as 1 mm-mrad while also decreasing the energy spread to half of its initial amount. The only drawback is the growth of final beam radius, which can be compensated by using a setting of quadrupole magnets.