| Paper | Title | Page |
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| MOPEA035 | Pulse Radiolysis with Supercontinuum Probe Generated by PCF | 145 |
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We have been studying a pump-probe pulse radiolysis as an application of the S-band photo cathode RF-Gun. Pump-probe spectroscopy is well-known method of pulse radiolysis measurement. We had used 5MeV electron beam obtained from the photo cathode RF-Gun as a pump beam, and used the white light emitted from Xe flash lamp or generated by self-phase modulation in the water cell as a probe light. However, the white probe light with high intensity, good stability and broad spectrum is a key issue for pump-probe pulse radiolysis. Supercontinuum light with photonic crystal fiber (PCF) is a new technique of white light generation. Short pulse laser through PCF spreads its spectrum by nonlinear optical effect. Supercontinuum light has very continuous spectrum, and it is studied for various applications recently. For applying supercontinuum light as a probe of pulse radiolysis experiment, we have generated a supercontinuum radiation with 7 picoseconds pulse width IR (1064nm) laser and PCF, and measured its properties. The experimental results of supercontinuum generation and design of a supercontinuum based pulse radiolysis system will be presented. |
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| TUPEC009 | Development of a Photocathode RF Gun for the L-band Linac at ISIR, Osaka University | 1728 |
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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. |
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| TUPE030 | High Power Terahertz FEL at ISIR, Osaka University | 2209 |
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We have been developing a Terahertz free electron laser (FEL) based on the 40 MeV, 1.3 GHz L-band electron linac at the Institute of Scientific and Industrial Research (ISIR), Osaka University. After the FEL lasing at the wavelength of 70 um (4.3 THz)*, next targets of the FEL development are to extend the available laser wavelength, to increase the FEL power, and to evaluate characteristics of FEL. Since the lowest energy of the linac was restricted by a fixed-ratio power divider between the acceleration tube and the buncher, we have prepared the new one with a different ratio to extend the wavelength longer side. As a result, the wavelength region is able to be extended to 25 - 147 um (12.5 - 2 THz). The maximum output energy of the FEL macropulse so far obtained is 3.6 mJ at 66 um. The peak macropulse power available to user experiments is estimated to be 1 kW or less, given that the pulse duration is 3 us. Three users groups have begun experiments using the FEL. We will report these recent activities on the Terahertz FEL. * G. Isoyama, R. Kato, S. Kashiwagi, T. Igo, Y. Morio, Infrared Physics & Technology 51 (2008) 371-374. |
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| WEPD030 | Elimination of Hall Probe Orientation Error in Measured Magnetic Field of the Edge-focusing Wiggler | 3159 |
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The edge-focusing (EF) wiggler has been fabricated to evaluate its performance rigorously with the magnetic field measurement. It is a 5-period planar wiggler with an edge angle of 2° and a period length of 60 mm. The magnetic field is measured using Hall probes at four different wiggler gaps. It is experimentally confirmed that a high field gradient of 1.0 T/m is realized, as designed, along the beam axis. The magnetic field gradient of the EF wiggler is derived as a function of the magnetic gap. The field gradient decreases with increasing magnet gap more slowly than the peak magnetic field does for the present experimental model. An analytic formula for the field gradient of the EF wiggler is derived and it is shown that the slope of the field gradient with the magnet gap can be changed by varying the magnet width of the EF wiggler. We analyzed the relation between the orientation errors of the measurement system and the measured magnetic field or field gradient using a model magnetic field of the EF wiggle. We corrected the measurement magnetic field based on this analysis and evaluated the performance of the EF wiggler. |
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| WEPD056 | Performance of the L-Band Electron Linac for Advanced Beam Sciences at Osaka University | 3221 |
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The 40 MeV L-band electron linac at the Institute of Scientific and Industrial Research, Osaka University is extensively used for various applications on advanced beam sciences including radiation chemistry by means of pulse radiolysis and development of the free electron laser in the THz region. It was constructed in 1975-78 and has been remodeled sometimes for improving its performance. The most recent one was made in 2002-2004 for higher operational stability and reproducibility, resulting in significant advances in the studies. We will report the present status of the linac and results of its performance evaluation. |
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| THPEC024 | Development of a High Average Power Laser Generating Electron Beam in ILC Format for KEK-STF | 4098 |
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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. |
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| THPEC031 | Multi-bunch Electron Beam Generation based on Cs-Te Photocathode RF-Gun at Waseda University | 4119 |
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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. |
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| MOPE019 | A Direct Measurement of the Longitudinal Phase Space for a Low Energy Electron Beam Using Energy Dependent Angular Distribution of Cherenkov Radiation | 1002 |
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A thermionic RF gun has been developed to generate very short electron bunch for a THz light source at Tohoku University. Bunch compression scheme requires, in general, linear momentum distribution of the particles with respect to the longitudinal position, so that measurement of longitudinal phase space is significant for better bunch compression. However, such measurement for the low energy electrons is difficult because space charge effect is so strong that longer drift space should not be included. Consequently, we have performed deliberation for employing energy dependent angular distribution of Cherenkov radiation. Though the energy dependence of emission angle of Cherenkov radiation is rapidly getting small as increasing the beam energy, it is still 25 deg/MeV at an energy around 2.0 MeV when we use radiator having refractive index of 1.035. Thus the beam energy distribution can be measured if we observe Cherenkov ring with sufficient angular resolution. Since this method needs only thin radiator, the drift space length will be minimized. We will discuss limitation for resolutions of both the time and the energy as well. |
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| TUPEC010 | Development of a Thermionic RF Gun for Coherent THz Source at Tohoku University | 1731 |
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A test accelerator for the coherent terahertz source (t-ACTS) has been under development at Laboratory of Nuclear Science, Tohoku University*. Intense coherent terahertz radiation will be generated by the very short electron bunch less than 100 fs using a thermionic RF gun (ITC RF-gun). ITC RF-gun is designed to have two cells uncoupled with each other, so that it can be operated at various combinations of different rf-power level and phase difference so as to optimize the longitudinal phase space distribution of the electron beam for bunch compression**. The gun employs single-crystal LaB6 cathode with small diameter of 1.8 mm to obtain a very small initial emittance with sufficiently high current density. The RF gun has been already manufactured and the measurement of RF characteristics is now in progress. We will present the results of low-power measurement and also discuss the effect of the cathode misalignment on the beam parameters such as transverse emittance and longitudinal phase space distribution. * H. Hama et al., New J. Phys. 8 (2006) 292. |