| Paper | Title | Page |
|---|---|---|
| WEPEB060 | System Design of Accelerator Safety Interlock for the XFEL/SPring-8 | 2827 |
|
||
|
The accelerator safety interlock system (ASIS) for the XFEL/SPring-8 protects personnel from radiation hazard. We designed the ASIS consisting of three independent systems; a central interlock system, an emergency interlock system and a beam route interlock system. The central interlock system monitors the machine tunnel security, status of beam line interlock system and radiation monitoring system. The emergency interlock system monitors status of emergency stop buttons. The beam route interlock system monitors electron beam route by inputting the current of the bending magnets at the electron-beam switching points. If any system trips, or if any system detects unsafe status, the permission signal for the accelerator operation from the system is off and the electron beam is inhibited. In addition, it is demanded that the permission signals must be transmitted within 16.6 ms. Therefore, the stability and fast response are required for the XFEL safety interlock system. We adopted programmable logic controllers (PLC) for the stability, and developed optical modules for the fast signal transmission. This paper describes system design of the ASIS. |
||
| WEPEB061 | A Fiber Beam Loss Monitor for the SPring-8 X-FEL: Test Operation at the SPring-8 250 MeV Compact SASE Source | 2830 |
|
||
|
Fiber-based beam loss monitors (BLM) have attracted much attention in recent years. Among them, systems using the detection of the Cerenkov light generated by the secondary charged particles hitting an optical fiber set along the vacuum chamber, offer the possibility to detect beam losses with a very fast response time (less than a few ms) over long distances, good position accuracy and sensitivity at a reasonable cost. For the undulator section of the SPring-8 X-FEL, radiation safety considerations set the desirable detection limit at 1 pC (corresponding to a 0.1% beam loss of the initial 1 nC/pulse) over more than a hundred meter. We report on a the test operation of a fiber-based BLM carried out at the 250 MeV SPring-8 Compact SASE Source (SCSS), a 1/16th model of the future X-FEL. The expected detection limit of the BLM based on a large (400 μm) core multimode fiber is below 2 pC over 120 m (for a corresponding 10 mV signal) while the position accuracy is expected to be better than one meter. |
||
| WEPEB062 | Fiber Beam Loss Monitor for the SPring-8 X-FEL: A Numerical Study of its Design and Performance | 2833 |
|
||
|
A fiber-based beam loss monitors (BLM) is under development for the undulator section of the SPring-8 X-FEL: the system is based on the detection of the Cerenkov light generated by the secondary charged particles hitting an optical fiber set along the vacuum chamber. Various parameters come into account in the final performance of the system, such as the impact angle and energy of the lost electrons, the fiber position (angular and radial) with respect to the point of impact, fiber characteristics (numerical aperture, index, diameter), etc. Thorough numerical studies have been carried out to investigate the performances of the system. Comparison with the experimental results obtained at the SPring-8 Compact SASE Source (SCSS), a 1/16th model of the future X-FEL are also given. |
||
| WEPEB063 | Concept of Radiation Monitoring and Safety Interlock Systems for XFEL/SPring-8 | 2836 |
|
||
|
The accelerator safety interlock system of XFEL/SPring-8 was designed to fulfill the requirement of matching with the safety interlock system of SPring-8 because both safety systems are planning to be unified in near future to deal with the electron beam injection from XFEL to SPring-8. At XFEL, however, additional requirements for the system also existed; the designed radiation shielding requires when the electrons are not injected into the dump core properly, the beam has to be terminated within 16 msec, which corresponds to 60 Hz operation, to avoid the next bunch coming. An outline of such different design criteria is presented together with the concept of the safety interlock system. The radiation monitoring system, which was also the same as that of SPring-8, was installed by reinforcing the redundancy and response time. Gamma and neutron monitors are set at 14 positions near the assumed loss points in the accessible place of the controlled area. The dose equivalent data are sent to the radiation monitoring systems of XFEL and SPring-8, respectively, and when the measured dose exceeds the preset level, an alarm signal is sent to the safety interlock promptly. |
||
| WEPEB068 | Feasibility Tests of the Beam Halo Monitoring System for Protecting Undulator Permanent Magnets against Radiation Damage at XFEL/SPring-8 | 2851 |
|
||
|
A beam halo region of an electron beam at a linear accelerator might hit the undulator magnets and degrade undulator permanent magnets. An interlock sensor is indispensable to protect the magnets against radiation damage. We have been developing an electron beam halo monitor using diamond detectors for an interlock sensor at the X-ray free electron laser facility at SPring-8 (XFEL/SPring-8). The diamond detectors are operated in photoconductive mode. Pulse-by-pulse measurements are adopted to suppress the background noise efficiently. The feasibility tests of this monitor have been performed at the SPring-8 compact SASE source (SCSS) test accelerator for XFEL/SPring-8, and the results will be summarized. |