Cold vacuum chamber for diagnostics: Analysis of the measurements at the Diamond Light Source and impedance bench measurements

Abstract

The beam heat load is an important input parameter needed for the cryogenic design of superconducting insertion devices. Theoretical models taking into account the different heating mechanisms of an electron beam to a cold bore predict smaller values than the ones measured with several superconducting insertion devices installed in different electron storage rings. In order to measure and possibly understand the beam heat load to a cold bore, a cold vacuum chamber for diagnostics (COLDDIAG) has been built. COLDDIAG is equipped with temperature sensors, pressure gauges, mass spectrometers as well as retarding field analyzers which allow to measure the beam heat load, total pressure, and gas content as well as the flux of particles hitting the chamber walls. COLDDIAG was installed in a straight section of the Diamond Light Source (DLS). In a previous paper the experimental equipment as well as the installation of COLDDIAG in the DLS are described [S. Gerstl et al., Phys. Rev. ST Accel. Beams 17, 103201 (2014)]. In this paper we present an overview of all the measurements performed with COLDDIAG at the DLS and their detailed analysis, as well as impedance bench measurements of the cold beam vacuum chamber performed at the Karlsruhe Institute of Technology after removal from the DLS. Relevant conclusions for the cryogenic design of superconducting insertion devices are drawn from the obtained results

Development and operating experience of a 1.1-m-long superconducting undulator at the Advanced Photon Source

“…It is difficult to compare the SCU1 heat load analysis with cryogenic devices elsewhere, given the markedly different geometry and vacuum elements. However, others have recently achieved similar agreement when detailed studies were carried out [16].…”

Cryogenic permanent magnet and superconducting undulators

“…Measurements for cross-checks are always welcome. A thorough study of heat dissipation effects dependent upon bunch length, bunch charge, and filling patterns was possible at DIAMOND utilizing the COLDDIAG setup [116] [117] [118]. In this specific case, RF losses due to geometric effects at imperfect thermal transitions were detected.…”

Beam-induced electron multipacting with mode resonance in a vacuum chamber

“…Figure 13 shows the E-field distributions in fundamental modes for the rectangular and elliptical vacuum chambers, respectively. In addition, the authors would like to remark that no pressure rise was observed and the absence of MP was proven by direct electron flux -12 -2021 JINST 16 P11001 measurements in warm and cold elliptical liners (Cu vacuum chambers) of the COLDDIAG (cold vacuum chamber for beam heat load diagnostics), developed at KIT, with electron beams at the DLS (Diamond Light Source) storage ring [32]- [34]. Our recent simulation results for the elliptical liner (a major axis of 30 mm, a minor axis of 5 mm, and a length of 490 mm) also showed no MP.…”