Status of Superconducting Cavities in LEP

The upgrade of the Large Electron Positron collider (LEP) with superconducting cavities is nearing a successful completion. There are presently 240 superconducting cavities installed which, together with the original copper RF system, provide up to 2.6GV per turn. The majority of the superconducting cavities is of niobium sputtered on copper and runs at an operating gradient of 6MV/m. In 1997, LEP has operated routinely at an energy of 91.5GeV per beam and with a total current of over 5mA. The operation of the RF system has been very satisfactory, with only a few cavities limited in field. This paper will concentrate on describing the operation of this system during 1997, including new features, operational procedures and present limitations. Future plans, notably the work towards improving performance and the installation of the remaining cavities, will also be covered

RF-Based Electron Beam Timing Measurement with Sub-10FS Resolution

Time of flight measurements of a relativistic electron beam have been performed and have demonstrated a resolution below 10 fs. The electronics consisted of a heterodyne receiver incorporating an array of analogue phase detectors in order to reduce noise. The performance of the system makes it suitable for the challenging requirements of intra-pulse train timing measurements in a future linear collider

Precision beam timing measurement system for CLIC synchronization

Very precise synchronization between main and drive beams is required in CLIC to avoid excessive luminosity loss due to energy variations. One possibility to accomplish this would be to measure and correct the drive beam phase. The timing reference for the correction could be the beam in the transfer line between the injector complex and the main linac. The timing of both main and drive beams will have to be measured to a precision in the region of 10 fs. The aim is to achieve this by means of a beam measurement at 30 GHz with the signal mixed down to an intermediate frequency (IF) for precise phase detection. The RF and IF electronics are being developed and tests will be carried out in CTF

CLIC Beam Position Monitor Tests

Prototype CLIC beam position monitors (BPMs) have been tested in the CLIC test facility (CTF) using a 50 MeV, 1 nC single bunch beam. The test set-up consisted of two BPMs and a charge normalization/phase reference cavity. The detection electronics consisted of a 5 channel super-heterodyne receiver to give charge independent horizontal and vertical positions in each BPM. Data were taken and processed at the full 10 Hz CTF repetition rate using a PC running LabVIEW. Both BPMs were mounted on 0.1 µm resolution micro-movers for displacement calibration. Separate tests in the lab of both cavities and electronics have shown that the potential resolution of the BPM system is less than one micron. An upper limit on resolution of ±4 µm has been demonstrated directly with the CTF beam. The measurement was almost certainly limited by the shot to shot angular jitter of the CTF beam

The performance of phaselocked loops for frequency control in single sideband land mobile radio receivers.

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