Abstracts Brochure - CERN

TUPCH — Poster Session 27-Jun-06 16:00 - 18:00
Characterization of the PEP-II Colliding-beam Phase Space by the Boost Method
We present a novel approach to characterize
the colliding-beam phase space at the inter- M. Weaver (SLAC) W. Kozanecki (CEA)
action point of the energy-asymmetric PEP-II
B-Factory. The method exploits the fact that the transverse-boost distribution of e + e − –> mu+ mu- events reconstructed
in the BaBar tracking system, reflects that of the colliding electrons & positrons. The average boost direction,
when combined with the measured orientation of the luminous ellipsoid, determines the e + e − crossing angles.
Varying the horizontal direction of one beam with respect to the other in a controlled fashion allows to estimate
the individual e + and e − horizontal IP beam sizes. The angular spread of the transverse boost vector provides an
accurate measure of the angular spread of the incoming high-energy beam, confirming the presence of a significant
beam-beam induced increase of this angular spread. In addition, the longitudinal dependence of the angular spread
of the boost vector in the y-z plane allows to extract from the continuously-monitored boost distributions, a weighted
average of the vertical IP beta-functions & emittances of the two beams representative of routine high-luminosity
operation.
Ion-related Phenomenon in UVSOR/UVSOR-II Electron Storage Ring
A vertical betatron tune shift depending on
beam current under multibunch condition
was observed in the UVSOR storage ring.
Vertical tune increased as beam current de-
A. Mochihashi, M. Hosaka, M. Katoh (UVSOR) Y. Hori (KEK) Y.
Takashima (Nagoya University)
creased, and the slope of the tune shift depended on the condition of the vacuum in the ring. Such a change in vertical
tune was explained by a change in the stability condition of trapped ions*/** with the beam current. Based on a
theoretical model*** that gives density of the trapped ions the experimental results were discussed via analytic and
tracking calculations. Both the effect from the residual gas ions generated by scattering between high energy electrons
and molecules and that from dissociated ions that come from secondary ionization processes have been discussed. In
quest of the ion-related phenomenon in single-bunch condition, precise tune measurement has been also performed
in the UVSOR-II storage ring. The experimental results in the single-bunch condition have been discussed. Precise
measurement of vacuum pressure in the beam duct is a key issue of the ion-related phenomenon. A design of vacuum
pressure measurement system via detecting residual gas fluorescence will be introduced in the presentation.
*R. D. Kohaupt. DESY Internal. Bericht No.H1-71/2 (1971). **Y. Baconnier and G. Brianti. CERN Internal Report
No.CERN/SPS/80-2(DI) (1980). ***A. Mochihashi et al. Jpn. J. Appl. Phys. 44 (2005) 430.
Upgrade of Main RF Cavity in UVSOR-II Electron Storage Ring
The UVSOR electron storage ring, which is
dedicated to a synchrotron radiation (SR)
light source especially for VUV and Soft Xray,
has been improved at the beginning of
A. Mochihashi, K. Hayashi, M. Hosaka, M. Katoh, J. Yamazaki
(UVSOR) H. Suzuki (Toshiba) Y. Takashima (Nagoya University)
2003, and transverse emittance in the improved ring (UVSOR-II)* has been decreased from 165nm-rad to 60 and/or
27nm-rad. Users runs have been performed since September 2003 with 60nm-rad mode, and since then high brilliant
SR beams have been supplied routinely for users. The 27nm-rad mode, however, was difficult to introduce to daily
operation initially because Touschek lifetime was insufficient in such small emittance condition. To improve the beam
lifetime and make full use of the SR beams, we have built new main RF cavity. The aim of the improvement was
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