Abstracts Brochure - CERN

TUPCH — Poster Session 27-Jun-06 16:00 - 18:00
Vacuum Issues and Challenges of SIS18 Upgrade at GSI
For the present experiment programm and
for the planned FAIR facility the heavy ion
synchroton SIS18 at GSI has to reach the
space charge limit for highly and interme-
H. Kollmus, M.C. Bellachioma, M. Bender, A. Kraemer, H.R.
Sprenger (GSI)
diate charged heavy ions. For the booster mode of SIS18 the number of 1x10 12 ions per second in 4 Hz operation
mode is specified. To achive this requirement a dynamic vacuum in the 10-12 mbar region has to be garanteed. The
poster will present the status of recent R & D work concerning the SIS18 vacuum upgrade, with a focus on the new
GSI NEG coating facility and on ion-induced desorption measurements using advanced ion beam analysis.
The Vacuum System of FAIR Accelerator Facility
The FAIR accelerator complex consists of
two superconducting synchrotrons (SIS100 A. Kraemer, H.R. Sprenger, St. Wilfert (GSI)
and SIS300) with a circumference of 1083.6m
each, a high energy beam transport system (HEBT) with a total length of about 2.5km and four storage rings (CR,
RESR, HESR and NESR). Their length varies between 200m and 550m. For each of the subsystems, different vacuum
requirements have to be fulfilled. The vacuum system of SIS100 and SIS300 consists of cryogenic and bakeable room
temperature sections, where a pressure in the lower 10-12 mbar range is needed. For HEBT, also a combination of
cryogenic and room temperature sections, a vacuum pressure of 10-9 mbar is sufficient. The storage rings will be
operated in a pressure range from 10-9 mbar to 10-12 mbar. In the poster a detailed layout of the vacuum systems
and technical solutions will be presented.
Wafer Preparation for the Photocathode Gun for the ERLP Project at Daresbury Laboratory
The Energy Recovery Linac Prototype
(ERLP) is a 35 MeV electron accelerator being
designed and built at Daresbury Laboratory.
The project combines ERL (energy recovery
K.J. Middleman, J.D. Herbert, L.B. Jones (CCLRC/DL/ASTeC) S.L.
Bennett (CCLRC/DL/SRD)
Linac) and FEL (free electron laser) technology to provide a flexible source of ultra-high brightness continuous and
pulsed FEL radiation in the range IR to XUV. The ERLP is well progressed with the first testing of certain accelerator
systems already under way. A key element of the accelerator is the DC photocathode electron gun operating at 350
kV. This source is a pre-requisite to generate the short-duration low-emittance electron bunches needed for optimum
performance of the FEL. The cathode material is a gallium arsenide (GaAs) semiconductor wafer, requiring careful
preparation to generate a Negative Electron Affinity (NEA) surface prior to use. The preparation stages comprise
cleaning by hydrogen ion bombardment, followed by cycles of caesiation and exposure to a reactive gas such as
nitrogen trifluoride or oxygen. To gain experience in the preparation of wafers for the ERLP project, a dedicated
vacuum system was constructed. This paper will describe the features of this new wafer preparation facility, inclu
211
TUPCH174
TUPCH175
TUPCH176