The conversion of CESR to operate as the Test Accelerator, CesrTA. Part 3: electron cloud diagnostics

Abstract

Cornell's electron/positron storage ring (CESR) was modified over a series of accelerator shutdowns beginning in May 2008, which substantially improves its capability for research and development for particle accelerators. CESR's energy span from 1.8 to 5.6 GeV with both electrons and positrons makes it ideal for the study of a wide spectrum of accelerator physics issues and instrumentation related to present light sources and future lepton damping rings. Additionally a number of these are also relevant for the beam physics of proton accelerators. This paper is the third in a series of four describing the conversion of CESR to the test accelerator, CESRTA. The first two papers discuss the overall plan for the conversion of the storage ring to an instrument capable of studying advanced accelerator physics issues[1] and the details of the vacuum system upgrades[2]. This paper focusses on the necessary development of new instrumentation, situated in four dedicated experimental regions, capable of studying such phenomena as electron clouds (ECs) and methods to mitigate EC effects. The fourth paper in this series describes the vacuum system modifications of the superconducting wigglers to accommodate the diagnostic instrumentation for the study of EC behavior within wigglers. While the initial studies of CESRTA focussed on questions related to the International Linear Collider damping ring design, CESRTA is a very versatile storage ring, capable of studying a wide range of accelerator physics and instrumentation questions.

Beam position monitoring system at CESR

“…The CESRTA project [1][2][3] required the development or upgrading of several systems involved in accelerator operations. In particular, a significant upgrade was needed for the beam position monitor (BPM) system, which replaced an original relay-based position monitor system.…”

The conversion of CESR to operate as the test accelerator, CesrTA, Part 4: superconducting wiggler diagnostics

“…There were also major vacuum system modifications to accommodate the changes in layout of the storage ring guide-field elements, to add electron cloud diagnostics and to prepare regions of the storage ring to accept beam pipes for the direct study of the electron cloud [2]. A large variety of instrumentation was also developed to support new electron cloud diagnostics, to increase the capabilities of the beam stabilizing feedback systems and the beam position monitoring system, to develop new X-ray beam size diagnostics and to increase the ability for studying beam instabilities [3]. This conversion process included the development of special instrumentation for the study of EC within superconducting wigglers and these are described in the following section.…”

“…In the CESR-c/CLEO-c era 12 home-built superconducting wigglers (SCWs) were installed in CESR [4], with two triplets at L1 and L5, two doublets and two singlet SCWs in the arcs (see Figure 1). This complement of SCWs plays an important role in the CESRTA program [1,2,3]. These SCWs additionally represent a good model for the wigglers planned for the International Linear Collider (ILC) damping rings [5].…”

Instrumentation for the study of low emittance tuning and beam dynamics at CESR

“…Each of these systems will be discussed in the following sections. Note that this paper is a companion to the set of papers describing the general modification of CESR's infrastructure to create the test accelerator CesrTA [1][2][3]. This paper is the concluding document in preliminary conference papers describing the instrumentation, required for the CesrTA Project in publications from workshops [13] and accelerator conferences [14][15][16] and within the CesrTA Phase 1 Report [4].…”

“…Some of the specific topics that were targeted for the initial phase of operation of the storage ring in this mode for CESR as a Test Accelerator (CesrTA) included 1) tuning techniques to produce low emittance beams, 2) the study of electron cloud development in a storage ring and 3) intra-beam scattering effects. The complete conversion of CESR to CesrTA occurred over a several year period, described elsewhere [1][2][3]. In addition to instrumentation for the storage ring, which was created for CesrTA, existing instrumentation was modified to facilitate the entire range of investigations to support these studies.…”