NSC/KIPT, Kharkov
KEK, Ibaraki
Nuclear resonance fluorescence (NRF) is the one of the most promising methods of the nuclear waste management and of the modern technologies of the nonproliferation of nuclear weapons. There are a few proposals of the usage of NRF *,**. Yet linac and energy recovery linac are suggested as the electron source for the Compton scattering (CS) of the laser photons. The storage ring is capable to produce sufficiently higher beam intensity and is more effective since the electrons interact with the laser pulse many times. The storage ring with the electron energy from 240 to 530 MeV is proposed for the CS of 1.16 eV laser photons in the report. Maximal energy of the scattered gamma rays lies within range from 1 MeV to 5 MeV. It allows detecting of practically any isotope in analyzed objects. The specificity of the proposed storage ring is usage of the crab-crossing of the electron and laser beams. Due to crab-crossing we expect to obtain the gamma beam intensity approximately 5*1013 gammas/s for laser flash energy 5 mJ stored in the optical cavity. Both electron beam and gamma beam parameters are studied analytically and by simulation of the CS in the designed ring lattice.
* J. Pruet et al. Detecting clandestine material with nuclear resonance fluorescence. J. Appl. Phys., 99, 123102-1-11 (2006).
** R. Hajima et al. J. Nucl. Sci. Tech., vol. 45, pp. 441-451, 2008.
KEK, Ibaraki
JAI, Egham, Surrey
OXFORDphysics, Oxford, Oxon
Optical Transition Radiation (OTR) appearing when a charged particle crosses a boundary between two media with different dielectric properties has widely been used as a tool for transverse profile measurements of charged particle beams in various facilities worldwide. The resolution of the conventional monitors is defined by so-called Point Spread Function (PSF) dimension - the source distribution generated by a single electron and projected by an optical system onto a screen. In our experiment we managed to create a system which can practically measure the PSF distribution. We demonstrated that is it is non-uniform. In this paper we represent the development of a novel sub-micrometer electron beam profile monitor based on the measurements of the PSF structure. The visibility of the structure is sensitive to micrometer electron beam dimensions. In this report we shall represent the recent experimental results. The future plans on the optimization of the monitor will also be presented.
KEK, Ibaraki
JAI, Egham, Surrey
INPR, Tomsk
TPU, Tomsk
RISE, Tokyo
High-brightness and reliable sources in the VUV and the soft X-ray region may be used for numerous applications in such areas as medicine, biology, biochemistry, material science, etc. 4th generation light sources based on X-ray free electron lasers are being built in a few world's leading laboratories. However, those installations are very expensive and the access to wider community is very limited. We propose a new approach to produce the intense beams of X-rays in the range of less than 500 eV based on compact electron accelerator. An ultimate goal of the project is to create a compact soft X-ray source based on Thomson scattering of Coherent Diffraction Radiation (CDR) using a small accelerator machine. CDR is generated when a charged particle moves in the vicinity of an obstacle. The radiation is coherent when its wavelength is comparable to or longer than the bunch length. The CDR waves will be generated in an opened resonator formed by two mirrors. In this report we represent the status of the experiment. The pilot experimental results and general hardware design will be demonstrated.
ICEPP, Tokyo
KEK, Ibaraki
University of Tokyo, Tokyo
In this paper, we describe a system design and current status of Shintake beam size monitor. Shintake monitor is a laser-based beam diagnostics tool, which provides a non-invasive measurement of transverse beam sizes. The interaction target probing the electron beam is interference fringes build up by the two coherent lasers that have narrow bandwidth and long coherent length. A scale of the target structure corresponds to approximately one fourth of the laser wave length, and the smallest measurable size reaches down to several tens of nanometers. The monitor we described here is installed at the virtual interaction point of the ATF2 beam line, which is built to confirm the proposed final focus system for Future Linear Colliders. We adopt second harmonics of Nd:YAG laser of 532 nm wavelength, and phase stabilization feedback system to allow to measure the designed beam size of about 37 nm. To widen a measurable range up to about 5 microns (wire scanner's range), we also prepare three crossing modes that change an effective wavelength for the fringes. The monitor is used to measure a focus size during the tuning process. The system is based on the Shintake monitor for FFTB.
University of Tokyo, Tokyo
KEK, Ibaraki
ICEPP, Tokyo
ATF2 is the final focus test facility for ILC to realize and demonstrate nanometer focusing. One of the goals of the ATF2 is a demonstration of a compact final focus system based on the local chromaticity correction. A designed beam size at the focal point is to be 37 nm in vertical. To achieve the goal, a beam size monitor capable of nanometer beam size measurement is inevitably needed. Shintake monitor satisfies the demands, and is installed at the virtual interaction point of the ATF2. Shintake monitor is a beam size monitor which uses laser interference fringe pattern to measure beam size. The beam test for the Shintake monitor was successful in measurement of signal modulation with the laser interference fringe pattern in November 2009. In April 2010, beam size of less than 1 micron was achieved. We have studied the error sources, and evaluated the total error to be less than 10% for 1 minute measurement. This paper is about the evaluation of the Shintake monitor performance by analyzing beam tests data. Most systematic error sources are well understood, so that we can estimate accuracy of beam size measurement when the beam size reaches 37nm.
KEK, Ibaraki
Sokendai, Ibaraki
RISE, Tokyo
Okayama University, Okayama
We have developed a compact X-ray source based on inverse Compton scattering of an electron beam and a laser pulse, which is stacked in an optical super-cavity, at LUCX accelerator in KEK. The accelerator consists of a photo-cathode rf-gun and an S-band accelerating tube and produces the multi-bunch electron beam with 100 bunches, 0.5nC bunch charge and 40MeV beam energy. It is planned to upgrade the accelerator and the super-cavity in order to increase the number of X-rays. A new RF gun with high mode separation and high Q value and a new klystron for the gun will be installed to provide good compensation with a high-intensity multi-bunch electron beam. A new optical super-cavity consisting of 4 mirrors is also being developed to increase the stacking power in the cavity and to reduce the laser size at the focal point. The first targets are to produce a multi-bunch electron beam with 1000 bunches, 0.5 nC bunch charge and 5 MeV beam energy in low energy mode and 100bunches, 2 nC and 40 MeV in high energy mode to generate X-rays by inverse Compton scattering. In this paper, the status and future plan of the accelerator will be reported.
NSC/KIPT, Kharkov
KEK, Ibaraki
CERN, Geneva
Compton sources are capable to produce intense beams of gamma-rays necessary for numerous applications, e.g. production of polarized positrons for ILC/CLIC projects, nuclear waste monitoring. These sources need high current of electron beams of GeV energy. Storage rings are able to accumulate a high average current and keep it circulating for a long time. The dynamics of circulating bunches is affected by large recoils due to emission of energetic photons. We report results of both an analytical study and a simulation on the dynamics of electron bunches circulating in storage rings and interacting with the laser pulses. The steady-state transverse emittances and energy spread, and dependence of these parameters on the laser pulse power and dimensions at the collision point were derived analytically and simulated. It is shown that the transverse and longitudinal dimensions of bunches are dependent on the power of laser pulses and on their dimensions as well. Conditions of the laser cooling were found, under which the electron bunches shrink due to scattering off the laser pulses. The beam behavior in rings with the longitudinal strong focusing lattices is discussed.
KEK, Ibaraki
The beam extraction experiment using the strip-line kicker has been carried out at KEK-ATF. The specification of the International linear collider (ILC) is that the long bunch train (1320 - 5120 bunches), which has the bunch spacing of 189 - 480ns, is compressed to 3 or 6ns bunch spacing into the DR, and again decompressed from the DR. The kicker manipulates the changes of the bunch spacing. The kicker requires a fast rise/fall time (3 or 6ns) and a high repetition rate (3 or 6MHz). A multiple strip-line kicker system is the most promising candidate to realize the specification for the ILC*. The beam extraction experiment at KEK-ATF** using proto-type of the strip-line kicker was done by following parameters, up to 30 bunches of the multi-bunch in the DR, which has 5.6ns bunch spacing, are extracted bunch-by-bunch with 308ns interval to the extraction line. The stored multi-bunch was extracted successfully. The detail of the experiment and the result are reported.
* T. Naito et. al., Proc. of PAC07, pp2772-2274.
** T. Naito et. al., Proc. of EPAC08, pp601-603.
JAI, Oxford
Royal Holloway, University of London, Surrey
KEK, Ibaraki
SLAC, Menlo Park, California
Kyungpook National University, Daegu
UCL, London
KNU, Deagu
Fermilab, Batavia
PLS, Pohang
The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a lepton linear collider. The ATF2 beam-line is instrumented with a total of 38 C and S band resonant cavity beam position monitors (BPM) with associated mixer electronics and digitizers. The current status of the BPM system is described, with a focus on operational techniques and performance.
ISIR, Osaka
KEK, Ibaraki
HU/AdSM, Higashi-Hiroshima
We conduct research on Free Electron Laser (FEL) in the infrared region and pulse radiolysis for radiation chemistry using the 40 MeV, 1.3 GHz L-band linac of Osaka University. At present, the L-band linac is equipped with a thermionic electron gun. It can accelerate a high-intensity single-bunch beam with charge up to 91 nC but the normalized emittance is large. In order to advance the research, we have begun development of a photocathode RF gun for the L-band electron linac in collaboration with KEK and Hiroshima University. We start the basic design of the RF gun cavity for the L-band linac at ISIR, Osaka University, based on the 1.5 cells, which is a normal conducting photocathode RF gun. A material of the cathode should be Cs2Te, which has the high quantum efficiency of a few percents, to produce a beam with high charge up to 30 nC/bunch. We improve the cooling system of the cavity for high duty operation to suppress the thermal deformation due to the heat load of input rf power. The simulation study has been also performed for the L-band linac at ISIR with a high charge electron beam. In this conference, we describe the details of the L-band photocathode RF gun development.
Sokendai, Ibaraki
KEK, Ibaraki
RISE, Tokyo
At Laser Undulator Compact Source (LUCX) at KEK, we designed and made a new RF Gun with high mode separation of 8.6 MHz and high Q value as compared to earlier guns. This paper presents fabrication details, low power measurements and tuning procedures followed in making the gun cavity. We also discuss in detail, experimentation done using this gun and show the measurement results. Currently we produce 100 bunch per train but we plan to go for 300 or more bunch per train operation. This will make possible to have higher charge available for laser-beam collisions to generate high flux soft X-rays by Inverse Compton Scattering at our setup.
ISIR, Osaka
KEK, Ibaraki
Both ultrafast time-resolved radiolysis and electron diffraction based on photocathode rf electron guns have been developed in Osaka University to reveal the hidden dynamics of intricate molecular and atomic processes in materials. One of the photocathode rf guns has been used successfully to produce a 100-fs high-brightness electron single bunch with a booster linear accelerator and a magnetic bunch compressor. The time resolution of 240 fs was achieved at the first time in the pulse radiolysis. Another photocathode rf gun, which produces directly a near-relativistic 100-fs electron beam, has been developed to construct femtosecond electron diffraction. The megavolt electron diffraction patterns have been observed. The dependences of the emittance, bunch length and energy spread on the radio-frequency (rf) and space charge effects in the rf gun were investigated.
RISE, Tokyo
KEK, Ibaraki
ISIR, Osaka
AIST, Tsukuba, Ibaraki
At Waseda University, we have been studying a high quality electron beam generation and its application experiments with Cs-Te photocathode RF-Gun. We have already succeeded in generating a stable high-charged single-bunch electron beam. To generate more intense electron beam, we designed a multi-bunch electron linac and developed the multi-pulse UV laser which irradiates to the cathode. The target values of the number of electron bunch and bunch charges are 100 bunches/train and 800 pC/bunch, respectively. In addition, we adopted the method of the amplitude modulation of the incident RF pulse to the S-band klystron in order to compensate the energy difference in each bunch because of the slow rise time of acceleration voltage in cavity and beam loading effect in the accelerating structure. In this conference, we will report design properties of our multi-bunch electron linac, the results of the multi-bunch electron beam diagnosis and the energy difference compensation using the RF amplitude modulation method.
CERN, Geneva
LAL, Orsay
KEK, Ibaraki
BNL, Upton, Long Island, New York
SLAC, Menlo Park, California
The current ATF2 Ultra-Low beta proposal was designed to achieve 20nm vertical IP beam size without considering the multipolar components of the FD magnets. In this paper we describe different scenarios that avoid the detrimental effect of these multipolar errors in the FD. The simplest approach consists in modifying the optics but other solutions are studied as the introduction of new higher order magnets or the replacement of the FD with SC technology. The practical aspects of such an upgrade are the tuning performance and the compatibility with existing devices and instrumentation. These are fully addressed in the paper.
BNL, Upton, Long Island, New York
LAL, Orsay
IN2P3-LAPP, Annecy-le-Vieux
OXFORDphysics, Oxford, Oxon
CERN, Geneva
KEK, Ibaraki
SLAC, Menlo Park, California
The KEK ATF2 facility, with a well instrumented beam line and Final Focus (FF), is a proving ground for linear collider (LC) technology to demonstrate the extreme beam demagnification and spot stability needed for a LC FF*. ATF2 uses water cooled magnets but the baseline ILC calls for a superconducting FF**. Thus we plan to replace some ATF2 FF magnets with superconducting ones made via direct wind construction as planned for the ILC. With no cryogenic supply at ATF2, we look to cool magnets and current leads with a few cryocoolers. ATF2 FF coil winding is underway at BNL and production warm magnetic measurements indicate good field quality. Having FF magnets with larger aperture and better field quality than present FF might allow reducing the beta function at the FF for study of focusing regimes relevant to CLIC. Our ATF2 magnet cryostat will have laser view ports for cold mass movement measurement and FF support and stabilization requirements under study. We plan to make stability measurements at BNL and KEK to relate ATF2 FF magnet performance to that of a full length ILC R&D prototype at BNL. We want to be able to predict LC FF performance with confidence.
* ATF2 proposal, volumes 1 and 2 at http://lcdev.kek.jp/ILC-AsiaWG/WG4notes/atf2/proposal/index.html
** International Linear Collider Reference Design Report, ILC-REPORT-2007-001, August 2007.
HU/AdSM, Higashi-Hiroshima
KEK, Ibaraki
ISIR, Osaka
IAP/RAS, Nizhny Novgorod
JINR, Dubna, Moscow Region
Aim of Super-conducting Test Facility (STF) at KEK is demonstrating technologies for International Linear Collider. In STF, one full RF unit will be developed and beam acceleration test will be made. In super-conducting accelerator, precise RF control in phase and power is essential because the input RF power should be balanced to beam accelerating power. To demonstrate the system feasibility, the beam accelerating test is an important step in R&D phase of STF and ILC. To provide ILC format beam for STF, we develop an electron source based on photo-cathode L-band RF gun. To generate ILC format beam, we developed a laser system based on Yb fiber oscillator in 40.6 MHz. The pulse repetition is decreased by picking pulses in 2.7 MHz, which meets ILC bunch spacing, 364 ns. The pulse is then amplified by YLF laser up to 8 uJ per pulse in 1 mm. The light is converted to 266 nm by SHG and FHG. Finally, 1.5 uJ per pulse is obtained and 3.2 nC bunch charge will be made. We report the basic performance of the laser system from the accelerator technology point of a view.