AVS 47th International Symposium
    Vacuum Technology Wednesday Sessions
       Session VT-WeP

Paper VT-WeP15
Experimental and Theoretical Study of a Differentially Pumped Absorption Gas Cell used as a Low Energy-pass Filter in the VUV Photon Energy Range

Wednesday, October 4, 2000, 11:00 am, Room Exhibit Hall C & D

Session: Poster Session
Presenter: B. Mercier, LURE, France
Authors: B. Mercier, LURE, France
L. Nahon, LURE, France
O. Dutuit, LURE, France
C. Prevost, LURE, France
R. Thissen, LURE, France
G. Bellec, LURE, France
M. Compin, LURE, France
Correspondent: Click to Email
In order to separate the fundamental synchrotron radiation from the high harmonics emitted by an undulator, a low photon energy-pass filter has been designed and built, insuring a high spectral purity on the VUV SU5 beamline at Super-ACO. It consists in an absorption cell filled with rare gases and separated from the ultra-high vacuum of the storage ring and of the beamline by a double differential pumping obtained with thin capillaries, and whose designed has been optimized by numerical computation of pumping speed. Admission pressures in the range of 100 Pa in the central part of the filter have used without any degradation of the upstream or downstream ultra-high vacuum. The measured attenuation factors above the energy cut-off are above 10@super 5@ and 10@super 2@ (and certainly above 10@super 3@ with ultimate pressure of Ne) for respectively argon and neon used as absorbing gas, with no measurable attenuation of fundamental radiation. A sophisticated numerical approach performed in the intermediate regime, taking into account the geometry of the whole absorption cell including the first pair of capillaries, has been developed, allowing reliable predictions of the expected attenuation coefficients for any given configuration of the filter.