CERN, Geneva
During the 2008 LHC injection synchronisation tests and the subsequent days with circulating beam, the majority of the LHC beam instrumentation systems were capable of measuring their first beam parameters. This included the two large, distributed, beam position and beam loss systems, as well as the scintillating and OTR screen systems, the fast and DC beam current transformer systems, the tune measurement system and the wire scanner system. The fast timing system was also extensively used to synchronise most of this instrumentation. This presentation will comment on the results to date, some of the issues observed and what remains to be done for the next LHC run.
PSI, Villigen
The resonant stripline pickup was chosen for a Beam Position Monitor (BPM) developed for the 250 MeV PSI XFEL Injector to reach the desired sensitivity of 10 micrometers in beam position. The electromagnetic design of this cavity, performed with Microwave Studio, was optimized in terms of the main radiofrequency characteristics - frequency, shunt impedance, Q value - of the resonant modes of interest, in order to obtain the pickup sensitivity required by the electronics (direct sampling, [*]). Also mechanical aspects of the design are presented, with particular attention to the solution adopted for the stripline alignment. Based on the simulated geometry, a pickup prototype was carried out and tested, allowing to verify the correct characteristics of the resonant modes and to state the present resonant stripline pickup design as one possible candidate for the standard (non-undulator) BPM system of the PSI XFEL and also for other linear accelerators or storage ring transfer lines.
[*]: B. Keil, S. Lehner. S. Ritt, "Application of a 5 GSPS Analogue Ring Sampling Chip For Low-cost Single-shot BPM Systems", Proc. EPAC 2008, Genoa, Italy, 1167 (2008).
DELTA, Dortmund
The beam orbit of the 1.5GeV electron storage ring DELTA showed a variety of beam distortions with a pronounced frequency spectrum mostly caused by girder movements and ripples of the magnet power supplies. In order to enhance the orbit stability at least up to 300 Hz bandwidth a global fast orbit feedback is under consideration. As a prototype an FPGA based local fast orbit feedback at a 10 kHz data acquisition rate has been developed. The digitized orbit data are distributed from I-Tech Libera and Bergoz MX-BPMs to an FPGA board via a fibre interconnected network based on the Diamond Communication Controller [*]. The correction algorithm is written in VHDL and the corrections are applied with digital power supplies connected to the FPGA board through RS485 links. The first operational tests of the system achieved an effective damping of orbit distortions up to 350 Hz. The paper will give an overview on the layout of the FPGA based local orbit feedback system, will report on the results of the measured uncorrected orbit distortions at DELTA and the stability enhancements that could be achieved by the local feedback system.
* I. S. Uzun et al., "Initial Design of the Fast Orbit Feedback System for
Diamond Light Source", Proc. 10th ICALEPCS
DESY Zeuthen, Zeuthen
LAL, Orsay
Research activities at the Photo Injector Test facility at DESY, Zeuthen site, (PITZ) aim to develop and optimize high brightness electron sources for Free Electron Lasers (FELs) like FLASH and the European XFEL. To demonstrate the XFEL operation, an electron bunch train containing 3250 pulses of 1 nC charge at 10 Hz repetition rate is required. The spectrometers and related equipments for studying the longitudinal phase space for such long pulse trains do not yet exist at PITZ. Design and construction of a new high energy dispersive arm (HEDA2) is currently in progress. Besides the requirement to handle long electron bunch trains, the HEDA2 setup is designed to allow high resolution measurements of momentum distribution up to 40 MeV/c, a longitudinal phase space measurement with slice momentum spread down to 1 keV/c and transverse slice emittance measurements at off crest booster phases. The status of the physics design and technical considerations of this dispersive section will be presented in this contribution.
INFN/LNF, Frascati (Roma)
INFN-Roma II, Roma
Rome University La Sapienza, Roma
ENEA C.R. Frascati, Frascati (Roma)
One of the key diagnostics techniques for the full characterization of beam parameters for LINAC-based FELs foresees the use of RF deflectors. With these devices it is possible to completely characterize both the longitudinal and the transverse phase space. In the talk I will present the main design considerations for time resolved (sliced) beam parameter measurements using RF deflectors. Measurement setups for longitudinal pulse shape as well as phase space and transverse beam slice emittance characterizations are described. The main sources of errors are discussed and the design criteria of these devices are presented. In particular the SPARC RF deflector and the related diagnostic lines as well as recent measurement results from the SPARC facility are shown. RF deflectors in use or planned to be used in other FEL labs are then illustrated with an overview of these activities.
ORNL, Oak Ridge, Tennessee
BINP SB RAS, Novosibirsk
An electron Scanner has been commissioned to non-destructively measure the transverse profiles in the Spallation Neutron Source (SNS) Ring. The SNS Ring is designed to accumulate in the order of 1.6·1014 protons with a typical peak current of over 50 Amps. Because of this high intensity no other profile measuring devices such as wire scanners were installed. The electron scanner is based on measuring the deflection of 50-75kV electrons by the electric field of the proton beam. Two electron guns, one for each plane, with dipole correctors, quadrupoles and deflectors to shape the electron beam have been installed. This paper describes the system and the initial results.
Fermilab, Batavia, Illinois
LBNL, Berkeley, California
Electron cloud density in the Fermilab Main Injector was measured by observing microwave transmission along the vacuum tube. Presence of the electron cloud reduces the velocity of the microwave signal. Both frequency and time domain methods reveal relative cloud density and time evolution. The effect of beam time structure is clearly evident. The accelerator magnetic field effects the distribution of electrons making it difficult to estimate density.
DESY, Hamburg
For current and future accelerators, in particular light sources, high availability is an important topic. Therefore the causes of beam losses must be diagnosed and eliminated as fast as possible. This paper presents a concept using the following signals and data from diagnostic instruments and other sources:
- software alarms transmitted by the control system,
- hardware alarms received and timestamped by the machine protection system, and
- Post-Mortem-Analysis.
IFIC, Valencia
A set of two Inductive Pick-Up (IPU) prototypes with its associated electronics for Beam Position Monitoring (BPM) in the Test Beam Line (TBL) of the 3rd Compact Linear Collider (CLIC) Test Facility (CTF3) at CERN were designed, constructed, and tested by the IFIC team. One prototype and two units of the series production are already installed in the TBL line. In the first part of the paper we describe the characterization tests of these two prototypes carried out at CERN, and the first beam tests performed to one of them. The second part of this paper is dedicated to the description of the issues addressed by the start of the series production and the characterization tests of the first series units performed with a custom-made low-frequency wire setup. This setup which emulates the beam position variation allows to carry out the series tests in an automatized manner and with higher accuracy.
PSI, Villigen
A new current monitor has been built and installed during the last maintenance period in prevision of the high intensity beam operation (3mA, 1.8MW) which is planned in the near future. It is a re-entrant cavity tuned at the 2nd RF harmonic (101 MHz). Compared to the current monitors already in operation, the design had to be modified to improve its cooling. Indeed, this monitor is placed 8 m behind a graphite target and is exposed to scattered particles. The resulting heat load would raise the monitor temperature well above 200 deg C without cooling. The modifications include a slightly different structure to improve the heat conduction, a blackening of the external surface to increase the thermal radiation and an active water cooling. Thermocouples placed on the cavity will monitor the temperature of the system. The new design was supported by simulations for heat load resulting from the scattered particles and by calculations concerning the cooling efficiency. Results obtained during laboratory tests and at the beginning of operation will be presented. Comparison between expected heat load and temperature with the actual measured values will be also discussed.
INFN/LNF, Frascati (Roma)
Università di Roma II Tor Vergata, Roma
INFN-Roma II, Roma
Rome University La Sapienza, Roma
ENEA C.R. Frascati, Frascati (Roma)
The characterization of the transverse phase space of electron beams with charge density and high energy is a fundamental requirement for particle accelerator facilities. The knowledge of characteristics of the accelerated electron beam is of great importance for the successful developement of the SPARC FEL. Here the high-energy emittance measurement with the quadrupole scan technique using two quadrupoles arranged as a doublet is discussed.