LINAC2012 - Classification: 04 Extreme Beams, Sources and Other Technologies / 4E Sources: Guns, Photo-Injectors, Charge Breeders

Paper

Title

Page

RF Photoinjector and Radiating Structure for High-power THz Radiation Source

86

S.M. Polozov, T.V. Bondarenko
MEPhI, Moscow, Russia
Y.A. Bashmakov
LPI, Moscow, Russia

Sources of high-power electromagnetic radiation in THz band are becoming promising as a new method of a low activation introscopy. Research and development of accelerating RF photoinjector and radiating system for THz radiation source are reported. The photoinjector is based on disk loaded waveguide (DLW). Two different designs of accelerating structures were modeled: widespread 1.6 cell of DLW structure and travelling wave resonator structure. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics and electric field distribution for all models were acquired. Results of picoseconds photoelectron beam dynamics in modeled structures are reported. Design of decelerating structures exciting Cherenkov radiation are based on corrugated metal channel and metal channel coated with dielectric. Analysis of radiation intensity and frequency band are presented.

TU3A03

First Electron Beam Operation of the LANL NCRF Photoinjector

N.A. Moody
LANL, Los Alamos, New Mexico, USA

The first ever photoelectron beam from LANL's cw normal-conducting radio-frequency (NCRF) injector has been observed. The NCRF injector at Los Alamos has produced its first continuous-wave photoelectron beam at energy up to 2 MeV and average current of a few mA. Accelerating gradients up to 10 MV/m at the cathode were confirmed with end-point x-ray energy measurements. The photoelectron beams were produced using both a continuous-wave blue laser diode and a cw modelocked green laser irradiating thin films of CsK₂Sb photocathodes deposited on a copper substrate. Both photocurrent and dark current were measured via a calibrated wall-current monitor, sensitive to a few μA levels. Preparation of CsK₂Sb photocathodes using chemical vapour deposition in an ultrahigh vacuum chamber and photocathode transfer to the NCRF injector will be described. We will also show the importance of the RF contact between the photocathode plug and the NCRF injector backplate for successful cw operation at high power.

Slides TU3A03 [1.755 MB]

THPLB12

Photoinjector SRF Cavity Development for BERLinPro

837

A. Neumann, W. Anders, T. Kamps, J. Knobloch
HZB, Berlin, Germany
E.N. Zaplatin
FZJ, Jülich, Germany

In 2010 HZB has received approval to build BERLinPro, an ERL project to demonstrate energy recovery at 100 mA beam current by pertaining a high quality beam. These goals place stringent requirements on the SRF cavity for the photoinjector which has to deliver a small emittance 100 mA beam with at least 1.5 MeV kinetic energy while limited by fundamental power coupler performance to about 200 kW forward power. In oder to achieve these goals the injector cavity is being developed in a three stage approach. The current design studies focus on implementing a normal conducting cathode insert into a newly developed superconducting photoinjector cavity. In this paper the fundamental RF design calculations concerning cell shape for optimized beam dynamics as well as SRF performance will be presented. Further studies concentrate on the HZDR based choke cell design to implement the high quantum efficiency normal conducting cathode with the SRF cavity.

Slides THPLB12 [1.431 MB]

THPB066

Photoinjector SRF Cavity Development for BERLinPro

993

A. Neumann, W. Anders, T. Kamps, J. Knobloch
HZB, Berlin, Germany
E.N. Zaplatin
FZJ, Jülich, Germany

In 2010 HZB has received approval to build BERLinPro, an ERL project to demonstrate energy recovery at 100 mA beam current by pertaining a high quality beam. These goals place stringent requirements on the SRF cavity for the photoinjector which has to deliver a small emittance 100 mA beam with at least 1.5 MeV kinetic energy while limited by fundamental power coupler performance to about 200 kW forward power. In oder to achieve these goals the injector cavity is being developed in a three stage approach. The current design studies focus on implementing a normal conducting cathode insert into a newly developed superconducting photoinjector cavity. In this paper the fundamental RF design calculations concerning cell shape for optimized beam dynamics as well as SRF performance will be presented. Further studies concentrate on the HZDR based choke cell design to implement the high quantum efficiency normal conducting cathode with the SRF cavity.

THPB068

First Observation of Photoemission Enhancement from Copper Cathode Illuminated by Z-Polarized Laser Pulse

996

H. Tomizawa, H. Dewa, A. Mizuno, T. Taniuchi
JASRI/SPring-8, Hyogo, Japan

Since 2006, we have developed a novel photocathode gun gated by laser-induced Schottky-effect. This new type of gun utilizes a laser’s coherency to aim at a compact femtosecond laser oscillator as an IR laser source using Z-polarization on the photocathode. This Z-polarization scheme reduces the laser photon energy (making it possible to excite the cathode with a longer wavelength) by reducing the work function of cathode due to Schottky effect. A hollow laser incidence is applied with a hollow convex lens in a vacuum that is focused after passing the laser beam through a radial polarizer. According to our calculations (convex lens: NA=0.15), a Z-field of 1 GV/m needs 1.26 MW at peak power for the fundamental wavelength (792 nm). In the first demonstration of Z-field emission, enhancement was done with a copper cathode at THG (264 nm). Consequently, we observed 1.4 times enhancement of photoemission at 1.6 GV/m of an averaged laser Z-field on the cathode surface. We report the first observation and analysis of the emission enhancements with this laser-induced Schottky-effect on metal copper photocathodes by comparing radial and azimuthal polarizations of the incident laser pulses.

THPB069

Beam Dynamics Studies for SRF Photoinjectors

999

T. Kamps, A. Neumann, J. Völker
HZB, Berlin, Germany

The SRF photoinjector combines the advantages of photo-assisted production of high brightness, short electron pulses and high gradient, low-loss continuous wave (CW) operation of a superconducting radiofrequency (SRF) cavity. The paper discusses beam dynamics considerations for FEL and ERL class applications of SRF photoinjectors. One case of particular interest is the design of the SRF photoinjector for BERLinPro, an ERL test facility demanding a high brightness beam with an emittance better than 1 mm mrad at 77 pC and average current of 100 mA.

THPB073

Initial RF Tests of the Diamond S-Band Photocathode Gun

1002

C. Christou, S.A. Pande
Diamond, Oxfordshire, United Kingdom

An S-band photocathode electron gun designed to operate at repetition rates up to 1 kHz CW has been designed at Diamond and manufactured at FMB*. The first test results of this gun are presented. Low-power RF measurements have been carried out to verify the RF design of the gun, and high-power conditioning and RF test has begun. Initial high power tests have been carried out at 5 Hz repetition rate using the S-band RF plant normally used to power the Diamond linac: the benefits and limitations of this approach are considered, together with plans for further testing.
* J. H. Han et al, NIM A 647(2011) 17-24

THPB074

RF Photoinjector and Radiating Structure for High-power THz Radiation Source

1005

S.M. Polozov, T.V. Bondarenko
MEPhI, Moscow, Russia
Y.A. Bashmakov
LPI, Moscow, Russia

Sources of high-power electromagnetic radiation in THz band are becoming promising as a new method of a low activation introscopy. Research and development of accelerating RF photoinjector and radiating system for THz radiation source are reported. The photoinjector is based on disk loaded waveguide (DLW). Two different designs of accelerating structures were modeled: widespread 1.6 cell of DLW structure and travelling wave resonator structure. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics and electric field distribution for all models were acquired. Results of picoseconds photoelectron beam dynamics in modeled structures are reported. Design of decelerating structures exciting Cherenkov radiation are based on corrugated metal channel and metal channel coated with dielectric. Analysis of radiation intensity and frequency band are presented.

Paper	Title	Page
SUPB035	RF Photoinjector and Radiating Structure for High-power THz Radiation Source	86
	S.M. Polozov, T.V. Bondarenko MEPhI, Moscow, Russia Y.A. Bashmakov LPI, Moscow, Russia
	Sources of high-power electromagnetic radiation in THz band are becoming promising as a new method of a low activation introscopy. Research and development of accelerating RF photoinjector and radiating system for THz radiation source are reported. The photoinjector is based on disk loaded waveguide (DLW). Two different designs of accelerating structures were modeled: widespread 1.6 cell of DLW structure and travelling wave resonator structure. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics and electric field distribution for all models were acquired. Results of picoseconds photoelectron beam dynamics in modeled structures are reported. Design of decelerating structures exciting Cherenkov radiation are based on corrugated metal channel and metal channel coated with dielectric. Analysis of radiation intensity and frequency band are presented.

TU3A03	First Electron Beam Operation of the LANL NCRF Photoinjector
	N.A. Moody LANL, Los Alamos, New Mexico, USA
	The first ever photoelectron beam from LANL's cw normal-conducting radio-frequency (NCRF) injector has been observed. The NCRF injector at Los Alamos has produced its first continuous-wave photoelectron beam at energy up to 2 MeV and average current of a few mA. Accelerating gradients up to 10 MV/m at the cathode were confirmed with end-point x-ray energy measurements. The photoelectron beams were produced using both a continuous-wave blue laser diode and a cw modelocked green laser irradiating thin films of CsK₂Sb photocathodes deposited on a copper substrate. Both photocurrent and dark current were measured via a calibrated wall-current monitor, sensitive to a few μA levels. Preparation of CsK₂Sb photocathodes using chemical vapour deposition in an ultrahigh vacuum chamber and photocathode transfer to the NCRF injector will be described. We will also show the importance of the RF contact between the photocathode plug and the NCRF injector backplate for successful cw operation at high power.
	Slides TU3A03 [1.755 MB]

THPLB12	Photoinjector SRF Cavity Development for BERLinPro	837
	A. Neumann, W. Anders, T. Kamps, J. Knobloch HZB, Berlin, Germany E.N. Zaplatin FZJ, Jülich, Germany
	In 2010 HZB has received approval to build BERLinPro, an ERL project to demonstrate energy recovery at 100 mA beam current by pertaining a high quality beam. These goals place stringent requirements on the SRF cavity for the photoinjector which has to deliver a small emittance 100 mA beam with at least 1.5 MeV kinetic energy while limited by fundamental power coupler performance to about 200 kW forward power. In oder to achieve these goals the injector cavity is being developed in a three stage approach. The current design studies focus on implementing a normal conducting cathode insert into a newly developed superconducting photoinjector cavity. In this paper the fundamental RF design calculations concerning cell shape for optimized beam dynamics as well as SRF performance will be presented. Further studies concentrate on the HZDR based choke cell design to implement the high quantum efficiency normal conducting cathode with the SRF cavity.
	Slides THPLB12 [1.431 MB]

THPB066	Photoinjector SRF Cavity Development for BERLinPro	993
	A. Neumann, W. Anders, T. Kamps, J. Knobloch HZB, Berlin, Germany E.N. Zaplatin FZJ, Jülich, Germany
	In 2010 HZB has received approval to build BERLinPro, an ERL project to demonstrate energy recovery at 100 mA beam current by pertaining a high quality beam. These goals place stringent requirements on the SRF cavity for the photoinjector which has to deliver a small emittance 100 mA beam with at least 1.5 MeV kinetic energy while limited by fundamental power coupler performance to about 200 kW forward power. In oder to achieve these goals the injector cavity is being developed in a three stage approach. The current design studies focus on implementing a normal conducting cathode insert into a newly developed superconducting photoinjector cavity. In this paper the fundamental RF design calculations concerning cell shape for optimized beam dynamics as well as SRF performance will be presented. Further studies concentrate on the HZDR based choke cell design to implement the high quantum efficiency normal conducting cathode with the SRF cavity.

THPB068	First Observation of Photoemission Enhancement from Copper Cathode Illuminated by Z-Polarized Laser Pulse	996
	H. Tomizawa, H. Dewa, A. Mizuno, T. Taniuchi JASRI/SPring-8, Hyogo, Japan
	Since 2006, we have developed a novel photocathode gun gated by laser-induced Schottky-effect. This new type of gun utilizes a laser’s coherency to aim at a compact femtosecond laser oscillator as an IR laser source using Z-polarization on the photocathode. This Z-polarization scheme reduces the laser photon energy (making it possible to excite the cathode with a longer wavelength) by reducing the work function of cathode due to Schottky effect. A hollow laser incidence is applied with a hollow convex lens in a vacuum that is focused after passing the laser beam through a radial polarizer. According to our calculations (convex lens: NA=0.15), a Z-field of 1 GV/m needs 1.26 MW at peak power for the fundamental wavelength (792 nm). In the first demonstration of Z-field emission, enhancement was done with a copper cathode at THG (264 nm). Consequently, we observed 1.4 times enhancement of photoemission at 1.6 GV/m of an averaged laser Z-field on the cathode surface. We report the first observation and analysis of the emission enhancements with this laser-induced Schottky-effect on metal copper photocathodes by comparing radial and azimuthal polarizations of the incident laser pulses.

THPB069	Beam Dynamics Studies for SRF Photoinjectors	999
	T. Kamps, A. Neumann, J. Völker HZB, Berlin, Germany
	The SRF photoinjector combines the advantages of photo-assisted production of high brightness, short electron pulses and high gradient, low-loss continuous wave (CW) operation of a superconducting radiofrequency (SRF) cavity. The paper discusses beam dynamics considerations for FEL and ERL class applications of SRF photoinjectors. One case of particular interest is the design of the SRF photoinjector for BERLinPro, an ERL test facility demanding a high brightness beam with an emittance better than 1 mm mrad at 77 pC and average current of 100 mA.

THPB073	Initial RF Tests of the Diamond S-Band Photocathode Gun	1002
	C. Christou, S.A. Pande Diamond, Oxfordshire, United Kingdom
	An S-band photocathode electron gun designed to operate at repetition rates up to 1 kHz CW has been designed at Diamond and manufactured at FMB. The first test results of this gun are presented. Low-power RF measurements have been carried out to verify the RF design of the gun, and high-power conditioning and RF test has begun. Initial high power tests have been carried out at 5 Hz repetition rate using the S-band RF plant normally used to power the Diamond linac: the benefits and limitations of this approach are considered, together with plans for further testing. J. H. Han et al, NIM A 647(2011) 17-24

THPB074	RF Photoinjector and Radiating Structure for High-power THz Radiation Source	1005
	S.M. Polozov, T.V. Bondarenko MEPhI, Moscow, Russia Y.A. Bashmakov LPI, Moscow, Russia
	Sources of high-power electromagnetic radiation in THz band are becoming promising as a new method of a low activation introscopy. Research and development of accelerating RF photoinjector and radiating system for THz radiation source are reported. The photoinjector is based on disk loaded waveguide (DLW). Two different designs of accelerating structures were modeled: widespread 1.6 cell of DLW structure and travelling wave resonator structure. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics and electric field distribution for all models were acquired. Results of picoseconds photoelectron beam dynamics in modeled structures are reported. Design of decelerating structures exciting Cherenkov radiation are based on corrugated metal channel and metal channel coated with dielectric. Analysis of radiation intensity and frequency band are presented.