Justin May

Photomultiplier Tubes in the MiniBooNE Experiment

The detector for the MiniBooNE [1] experiment at the Fermi National Accelerator Laboratory employs 1520 8 inch Hamamatsu models R1408 and R5912 photomultiplier tubes with custom-designed bases. Tests were performed to determine the dark rate, charge and timing resolutions, double-pulsing rate, and desired operating voltage for each tube, so that the tubes could be sorted for optimal placement in the detector. Seven phototubes were tested to find the angular dependence of their response. After the Super-K phototube implosion accident, an analysis was performed to determine the risk of a similar accident with MiniBooNE.

Cavity beam position monitor system for the Accelerator Test Facility 2

The Accelerator Test Facility 2 (ATF2) is a scaled demonstrator system for final focus beam lines of linear high energy colliders. This paper describes the high resolution cavity beam position monitor (BPM) system, which is a part of the ATF2 diagnostics. Two types of cavity BPMs are used, C-band operating at 6.423 GHz, and S-band at 2.888 GHz with an increased beam aperture. The cavities, electronics, and digital processing are described. The resolution of the C-band system with attenuators was determined to be approximately 250 nm and 1 � m for the S-band system. Without attenuation the best recorded C-band cavity resolution was 27 nm.

High precision SC cavity alignment measurements with higher order modes

Experiments at the FLASH linac at DESY have demonstrated that the higher order modes (HOMs) induced in superconducting cavities can be used to provide a variety of beam and cavity diagnostics. The centers of the cavities can be determined from the beam orbit which produces minimum power in the dipole HOM modes. The phase and amplitude of the dipole modes can be used as a high resolution beam position monitor. For most superconducting accelerators, the existing HOM couplers provide the necessary signals, and the downmix and digitizing electronics are straightforward, similar to those for a conventional BPM.

Electronics and Algorithms for HOM Based Beam Diagnostics

The signals from the Higher Order Mode (HOM) ports on superconducting cavities can be used as beam position monitors and to do survey structure alignment. A HOM-based diagnostic system has been installed to instrument both couplers on each of the 40 cryogenic accelerating structures in the DESY TTF2 Linac. The electronics uses a single stage down conversion form the 1.7 GHz HOM spectral line to a 20MHz IF which has been digitized. The electronics is based on low cost surface mount components suitable for large scale production. The analysis of the HOM data is based on Singular Value Decomposition. The response of the OM modes is calibrated using conventional BPMs.