Abstracts Brochure - CERN

TUPCH — Poster Session 27-Jun-06 16:00 - 18:00
flange, a bellows chamber and a gate valve with the same cross section to the beam duct, were also developed and
tested together with the beam duct.
Experimental Study of NEG-coated Vacuum Chamber at Different Temperatures under SR
Irradiation
The coating of vacuum chambers with TiZrV
non-evaporable getter (NEG), developed at R.V. Dostovalov, V.V. Anashin, A.A. Krasnov (BINP SB RAS)
CERN, is an attractive pumping technology
for a vacuum chamber of particle accelerators. The NEG coating, once activated, is an attractive material since apart
from providing a distributed pumping, it may inhibit the gas desorption from the vast reservoir of the industrially
prepared substrate material. The NEG coated vacuum chambers are planed to use at room temperature in LHC
(CERN). A present work includes the advanced study of NEG properties under Synchrotron Radiation (SR) irradiation
at temperatures in the range from 293 to 90 K. The work was performed at BINP with using of SR from VEPP-3 storage
ring. The main result is that dynamic pressure and desorption of H2 inside NEG coated chamber at 90 K are
significantly less than ones at room temperature.
Radiation Monitors as a Vacuum Diagnostic in the Room Temperature Parts of the LHC
Straight Sections
In the absence of collisions, inelastic interactions
between protons and residual gas mol- V. Talanov (IHEP Protvino) V. Baglin, T. Wijnands (CERN)
ecules are the main source of radiation in the
room temperature parts of the LHC long straight sections. In this case the variations in the radiation levels will reflect
the dynamics of the residual pressure distribution. Based on the background simulations for the long straight section
of the LHC IP5 and on the current understanding of the residual pressure dynamics, we evaluate the possibility to use
the radiation monitors for the purpose of the vacuum diagnostic, and we present the first estimates of the predicted
monitor counts for different scenarios of the machine operation.
H2 Equilibrium Pressure in a NEG-coated Vacuum Chamber as a Function of Temperature
and H2 Concentration
Non Evaporable Getter (NEG) coating is used
in the LHC room- temperature sections to en- A. Rossi (CERN)
sure a low residual gas pressure for its properties
of distributed pumping, low outgassing and desorption under particle bombardment; and to limit or cure
electron cloud build-up due to its low secondary electron emission. In certain regions of the LHC, and in particular
close to the beam collimators, the temperature of the vacuum chamber is expected to rise due to energy deposition
from particle losses. Gas molecules are pumped by the NEG via dissociation on the surface, sorption at the superficial
sites and diffusion into the NEG bulk. In the case of hydrogen, the sorption is thermally reversible, causing the
residual pressure to increase with NEG temperature and amount of H2 pumped. Measurements were carried out on
a stainless steel chamber coated with TiZrV NEG as a function of the H2 concentration and the chamber temperature,
to estimate the residual gas pressure in the collimator regions for various LHC operation scenarios, corresponding
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