56 research outputs found
Empirical comparison of high gradient achievement for different metals in DC and pulsed mode
For the SwissFEL project, an advanced high gradient low emittance gun is
under development. Reliable operation with an electric field, preferably above
125 MV/m at a 4 mm gap, in the presence of an UV laser beam, has to be achieved
in a diode configuration in order to minimize the emittance dilution due to
space charge effects. In the first phase, a DC breakdown test stand was used to
test different metals with different preparation methods at voltages up to 100
kV. In addition high gradient stability tests were also carried out over
several days in order to prove reliable spark-free operation with a minimum
dark current. In the second phase, electrodes with selected materials were
installed in the 250 ns FWHM, 500 kV electron gun and tested for high gradient
breakdown and for quantum efficiency using an ultra-violet laser.Comment: 25 pages, 13 figures, 5 tables. Follow up from FEL 2008 conference
(Geyongju Korea 2008) New Title in JVST A (2010) : Vacuum breakdown limit and
quantum efficiency obtained for various technical metals using DC and pulsed
voltage source
Luminosity Upgrades For The Slc
Recent performance improvements at the SLAC Linear Collider (SLC) have led to a proposal to further increase the luminosity up to a factor of four through a series of modest hardware upgrades. New final focus optics introduced in 1997 combined with permanent magnet octupoles have reduced the contribution to the final beam size due to higher order aberrations. The minimum betas achievable at the IP are presently limited by the increase in detector backgrounds as the beam is focused more strongly. By moving the final quadrupoles closer to the interaction point (IP), one can reduce the synchrotron radiation background while decreasing the IP betas. Other upgrades include increasing the bending radius in the final focus to minimize emittance dilutions due to synchrotron radiation, a fast feedforward from the linac to the final focus to cancel trajectory jitter, and a change in the horizontal damping ring partition number to reduce the emittance of the extracted beam. With these upgrades, t..
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