wg2 summary: diagnostics, measurements, and...
TRANSCRIPT
WG2 Summary:Diagnostics, measurements, and
commissioning
Aaron TremaineSteve Lidia
And a host of others who shall remain blameless.
WG2 discussions
Talks given
High brightness measurements, e.g. LCLS (~kW)
High current measurements leading to MWAssume bunch train
Commissioning
all for Q = 1 nC
0.8
1.2
1.6
2.0
2.4
2.8
3.2
0 3 6 9 12 15 18 21 24 27 30
Ibuck, A
no
rm.
em
itta
nc
e /
mm
m
rad Ex
EySQRT(Ex*Ey)
Φ = Φm – 5°
Imain = 326 A
20. 8. 2004
0.8
1.2
1.6
2.0
2.4
2.8
3.2
320 322 324 326 328 330
Imain, A
no
rm. em
itta
nce / m
m m
rad Ex
EySQRT(Ex*Ey)
Φ = Φm
Ibuck = Imain * 0.075
24. 8. 2004
VUV-FEL (30 nm)
VUV-FEL (6 nm)
XFEL
• min. emittance improved
• geom. average improved
• still a long way to go for XFEL requirements !
Transverse Emittance measurements
Courtesy A. Oppelt
Determine Longitudinalφ-Space at Linac Entrance
Measure Energy Spectra vs linac phaseLinear analysis allows only linear time energy correlationsFit τ11, τ12, τ22, Vlinac, and θlinac
Quad scan and fit Twiss parameters
Technique analagous to quadrupole scan of transverse emittance
Longitudinal Emittance Measurement
3 m linac(vary φlinac)
GunSpectrometer
Energy Screen
QuadDoublet
Courtesy, J. Schmerge
1. ImplementationTV & Streak-camera
Magnetic Kicker
~100 us~1-2 us
10 W0.1 W
t
E-beam
Phosphor + OTR
Ti Foil
Vacuum chamber
Courtesy Timur Shaftan
UCLA/ATF chicane compressionexperiments
• Extend UCLA chicane experimentsto regime with significantacceleration-field
• Chicane designed, fabricated andcharacterized at UCLA
• Extensive simulation work• Coherent radiative effects central to
mission• Add to ATF core capabilities…
– SASE FEL– Wakefield studies
Coherent radiationexit port
Bunch length diagnostic comparison
NoNoRelativeNoYesEnergyWake-loss
NoYesAbsoluteYesNoElectro OpticSampling
NoNoAbsolute(2nd moment
only)
NoNo for CSRYes for CTR
CoherentRadiationAutocorrelation
YesNoRelativeYesNo for CSRYes for CTR
CoherentRadiationSpectral power
NoNoAbsoluteNo: 3 pulsesYes: Steal 3pulses
RF TransverseDeflectingCavity
Detectµ bunching
Timingmeasurement
Abs. or rel.measurement
Single shotmeasurement
Invasivemeasurement
Device Type
Courtesy Patrick Krejcik
High Brightness, <5kW
Word document
Average Power ->1 MW
Measurements of single bunches interesting, but not necessary(assuming high brightness bunches)
Invasive is not robust solution, water cooled OTR good to several kW
Kick out several pulses and make measurements
Consult Damping Ringers for kicker specs
Commissioning
Common problem -Not enough diagnostics near source/low energyReal estateBeam dynamics
Low rep rate & charge start, ramp up to high rep rate & chargeWatch for changing source physics
When low ε important, source very important
Usually diagnose source on test stand and installMeasurements downstream, hard to diagnose source again
Halo & beam loss
For MW beam, 10 kW halo conceivableWith wire scanner progressively measure haloTry to remove at low energy (lower power)Scrappers
Where does halo form? Simulations?
Beam lossRadiation detector schemes, LC community
Look to LC for collimation schemes, takes a lot of beamline
Other issues
2 screen OTR emittance, useful > 15 MeV
Are there situations where you need to know more than our list?User definedMulti-channel striplines, higher order content
Radiation environment in high current scenarioX-ray damage to equipmentAre diagnostics/electronics reliable