Abstracts Brochure - CERN

TUPCH144
TUPCH145
TUPCH146
27-Jun-06 16:00 - 18:00 TUPCH — Poster Session
Automatic Conditioning of the CTF3 RF System
J.P.H. Sladen, S. Deghaye, S. Livesley, J. Marques Balula, J. Mourier,
J.-M. Nonglaton (CERN) A. Dubrovsky (JINR)
202
The RF system of CTF3 (CLIC Test Facility 3)
includes ten 35 MW to 40 MW 3 GHz klystrons
and one 20 MW 1.5 GHz klystron.
High power RF conditioning of the wave-
guide network and cavities connected to each klystron can be extremely time consuming. Because of this, a fully
automatic conditioning system has been developed within a CERN JINR (Dubna) collaboration. It involves relatively
minor hardware additions, most of the work being in application and front-end software. The system has been used
very successfully.
The MUCOOL RF Program
J. Norem (ANL) A. Bross, A. Moretti, B. Norris, Z. Qian (Fermilab)
D. Li, S.P. Virostek, M.S. Zisman (LBNL) R.A. Rimmer (Jefferson
Lab) Y. Torun (IIT)
Efficient muon cooling requires high RF gradients
in the presence of high (∼3T) solenoidal
fields. The Muon Ionization Cooling
Experiment (MICE) also requires that the xray
production from these cavities is low, in
order to minimize backgrounds in the particle detectors that must be located near the cavities. These cavities require
thin Be windows to ensure the highest fields on the beam axis. In order to develop these cavities, the MUCOOL
RF Program was started about 6 years ago. Initial measurements were made on a six-cell cavity and a single-cell
pillbox, both operating at 805 MHz. We have now begun measurements of a 201 MHz pillbox cavity. This program
has led to new techniques to look at dark currents, a new model for breakdown and a general model of cavity performance
based on surface damage. The experimental program includes studies of thin Be windows, conditioning,
dark current production from different materials, magnetic-field effects and breakdown. We will present results from
measurements at both 805 and 201 MHz.
The Effects of Surface Damage on RF Cavity Operation
J. Norem, A. Hassanein, Z. Insepov (ANL) A. Bross, A. Moretti, Z.
Qian (Fermilab) D. Li, M.S. Zisman (LBNL) R.A. Rimmer (Jefferson
Lab) D.N. Seidman, K. Yoon (NU) Y. Torun (IIT)
Studies of low frequency RF systems for
muon cooling has led to a variety of new
techniques for looking at dark currents, a
new model of breakdown, and, ultimately,
a model of RF cavity operation based on sur-
face damage. We find that cavity behavior is strongly influenced by the spectrum of enhancement factors on field
emission sites. Three different spectra are involved: one defining the initial state of the cavity, the second determined
by the breakdown events, and the third defining the equilibrium produced as a cavity operates at its maximum
field. We have been able to measure these functions and use them to derive a wide variety of cavity parameters:
conditioning behavior, material, pulse length, temperature, vacuum, magnetic field, pressure, gas dependence. In
addition we can calculate the dependence of breakdown rate on surface field and pulse length. This work correlates
with data from Atom Probe Tomography. We will describe this model and new experimental data.