ILC Beam Switchyard Update

1
ILC Beam Switchyard Update
M. Woodley, September 6, 2005
2
BSY Diagnostic Chicane Issues Questions (M.
Woodley, August 25, 2005)
-
functional requirements 1) detection of
off-energy bunches and abort triggering 2)
location of detectors for BSY diagnostic section
laserwires 3) measurement of energy and energy
spread - issues 1) distance from energy BPM
to FEXL kickers (how many bunches get through?)
2) ISR emittance growth 3) total chicane
length 4) magnet technology (H-bends?
C-bends?) 5) energy offset resolution 6)
resolution of dispersion/betatron motion
discrimination 7) minimum beam size for
laserwire 3 um 8) need vacuum window and
line-of-sight to laserwire photon detectors(one
near center of chicane for upstream
emittance laserwires, one after central chicane
bends for energy spread laserwire) 9) minimum
clearance for laserwire detectors 1 inch -
beam parameters 1) normalized emittance emitxn
10e-6 m 2) energy spread (dP/P) 0.06 _at_
250 GeV, 0.03 _at_ 500 GeV (PT) 3) minimum
dispersion determines chromatic spot size ...
etax 20 mm gives 12 um _at_ 250 GeV, 6 um _at_ 500
GeV 4) for energy spread resolution, need
geometric spot size (at most) equal to chromatic
spot size ... betax 5 m gives 10.1 um _at_
250 Gev, 7.1 um _at_ 500 GeV 5) sigmax 15.7 um _at_
500 GeV, 9.3 um _at_ 500 GeV - questions/comments
1) ISR emittance growth limits 1 _at_ 500 GeV?
0.1 ? 1 _at_ 250 GeV? 2) kickers in 2nd leg of
chicane? (issue 1) ... if so, must have QD (or no
quad at all) at exit of chicane which makes
optics tricky given 5 m betax at center of
chicane and chicane length needed to preserve
emittance 3) quadrupoles in chicane? 4) "bad
beam" threshold - 2 dP/P, 25 sigmax _at_ 250 GeV,
43 sigmax _at_ 500 GeV 5) threshold for incoming
betatron oscillations?
3
vacuum chamber ?15 mm
laserwire photons go through here
Bretts BMP magnet has a wide (28 mm) clear
horizontal aperture put in a small (but
reasonable) vacuum chamber for the beam and use
the reamining clear aperture to pass laserwire
photons
4
total length 111.1 m
laserwire detector (sd)
energy BPM, laserwire (sd)
?E/E 20 trajectories
window
?
clearance12.5 mm
vacuum chamber ?15 mm
?
window
laserwire detector (e)
Brett Parkers BMP dipoles (20)
5
(No Transcript)
6

• length of chicane, required beam waist at central
  laserwire, and maximum beta at the waist means
  kilometer-size beta at beginning and end of
  chicane still looking for matching solution for
  non-extracted beam
• matching problems might push me away from having
  kickers in the chicane, so kickers would then
  start just downstream of the chicane delay time
  is 50 ns (assuming a cable signal velocity of
  0.8c)
• I need to know a reasonable kick angle per unit
  length, given the required temporal properties of
  the kicker/pulser combination (TDR 5.3 µrad/m
  (scaled to 500 GeV beam) BP 40 µrad/m)