TY - CPAPER
AU - Miura, A.
AU - Kawane, Y.
AU - Miyao, T.
AU - Ouchi, N.
TI - Vacuum Improvement of Bunch Shape Monitor for J-PARC Linac
J2 - Proc. of IBIC2014
AB - During the shutdown in summer 2012, we installed three BSMs (Bunch Shape Monitors) at the upstream of the ACS (Annular Coupled Structure Linac) section in order to perform longitudinal matching. ACS cavities were installed in summer 2013 to upgrade the Linac energy from 181 MeV to 400 MeV. Prior to the ACS installation, BSMs were installed and the beam commissioning of the BSMs has been conducted after the summer shutdown in 2012. During the BSM measurements, a problem of the degradation in vacuum conditions was found. One reason for this problem is the dark current resulting in the desorption of absorbed gas molecules. And another reason is the outgas released from materials when the high voltage and RF power are supplied for the electro-static lens and RF deflector, respectively. In order to solve this problem, BSMs were dismounted from the beam line and the off-line baking operations with outgas analysis had been performed to avoid the degradation of the vacuum. As the result of the gas analysis, we found that the outgas contains some heavy hydrocarbons. After these heavy hydrocarbon gaseous were removed and the vacuum level improved for about one order, we completed off-line baking. We will install all three BSMs in at the upstream of the ACS again with the additional vacuum pumps. This paper describes the vacuum degradation of the BSMs, how to conduct the baking operation for BSMs and its results. The improved set-ups of the vacuum are also introduced.
PB - JACoW
CY - Geneva, Switzerland
SP - 430
EP - 434
KW - vacuum
KW - target
KW - high-voltage
KW - electron
KW - linac
DA - 2014/10
PY - 2014
SN - 978-3-95450-141-0
UR - http://jacow.org/IBIC2014/papers/tupd09.pdf
ER -