Abstracts Brochure - 2nd International Particle Accelerator Conference

�
Post Deadline Inclusion in Student Poster Session
In Classifications 02 and 07
Poster Panel 128
Classification 02 Synchrotron Light Sources and
FELs/T02 Lepton Sources
ID: 3953 - THPC117
Analysis Quantum Efficiency Spectrum of NEA-
GaAs Photocathode, Yuki Masumoto (HU/AdSM,
Higashi-Hiroshima) - ERL is a future project of
synchrotron light source with high brightness and
partial coherence. ERL is based on super conducting
linear accelerator providing the high brightness
electron beam to insertion devices continuously.
One of the most difficult technical challenge is the
electron source for ERL. A photo-cathode DC
biased gun is assumed, but several issues should be
solved. One of the issue is the operational lifetime of
cathode material, NEA GaAs. NEA stands for
Negative electron affinity made by artificial
treatment on clean GaAs surface. Emission from the
cathode is decreased in time and extracted beam
current. In order to research the phenomena, the
surface potential is studied by measuring the QE
(Quantum Efficiency) spectrum. Observing temporal
evolution of QE, we found that the photon energy
threshold did not change during the decay. The
spectrum shape was changed suggesting that the
surface potential barrier becomes thicker.
39
Poster Panel 129
Classification 07 Accelerator Technology/T07
Superconducting RF
ID: 3322 - MOPC102
RF and Surface Properties of Superconducting
Samples, Tobias Junginger (CERN, Geneva;
MPI-K, Heidelberg), Wolfgang Weingarten
(CERN, Geneva), Carsten Peter Welsch (Cockcroft
Institute, Warrington, Cheshire; The University of
Liverpool, Liverpool), Rebecca Seviour (Lancaster
University, Lancaster) - The surface resistance Rs of
superconducting cavities can be obtained from the
unloaded quality factor Q0. Since Rs varies strongly
over the cavity surface its value must be interpreted
as averaged over the whole cavity surface. A more
convenient way to investigate the surface resistance
of superconducting materials is therefore to examine
small samples, because they can be manufactured
cheaply, duplicated easily and used for further
surface analyses. At CERN a compact Quadrupole
Resonator has been developed for the RF
characterization of superconducting samples at
different frequencies. In this contribution, results
from measurements on bulk niobium and niobium
film on copper samples are presented. It is shown
how different contributions to the surface resistance
depend on temperature, applied RF magnetic field
and frequency. Furthermore, measurements of the
maximum RF magnetic field as a function of
temperature and frequency in pulsed and CW
operation are presented. The study is accompanied
by measurements of the surface properties of the
samples by various techniques.
Work supported by the German Doctoral Students
program of the Federal Ministry of Education and
Research (BMBF)