R Apsimon Lancaster University Cockcroft Institute Motivation Currently bunch length and energy spread measurements done with separate diagnostics Cant reconstruct the longitudinal phase space ID: 786164
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Slide1
An X-band transverse deflecting cavity for longitudinal phase space measurements
R. Apsimon
Lancaster University / Cockcroft Institute
Slide2Motivation
Currently bunch length and energy spread measurements done with separate diagnostics
Can’t reconstruct the longitudinal phase space
No way to measure correlation between longitudinal position and momentum
Upgrade existing spectrometer for AWAKE
Currently only able to measure energy/momentum spectrum of the beam
Transverse deflecting cavity (TDC) to perform full phase space measurement
Can obtain slice energy spread along the longitudinal profile
Slide3Brief description of proposed concept
Current scheme:
Dipole used to deflect electron beam horizontally
Introduces dispersion: different momenta have different horizontal position
iCCD camera used to measure distribution on screen
Proposed scheme:
Add a TDC upstream of dipole to deflect vertically
Time is mapped onto the vertical axis of the screen
momentum on the horizontal axis
Allows the longitudinal phase space of the beam to be measured
Slide4Brief description of the proposed concept
Current layout
Proposed layout
Slide5Experience with VELA
Daresbury Laboratory and Cockcroft Institute have experience of using a TDC for diagnostics on VELA
TDC off
TDC on
Slide6Preliminary specifications
Parameter
Value
Bunch length
~4 ps
Target
time resolution
~100
fs
Beam energy
~2 GeV
Distance:
TDC to screen
~10
m
Vertical
beam size at screen
~1 mm
Required peak transverse voltage (at 12 GHz)~53 MV*Required peak transverse voltage (at 3 GHz)~212 MV*Transverse voltage (assuming CLIC parameters)~ 10 MV/m of cavity length
*This assumes only a drift length between the TDC and the screen.
Further studies needed to see how much the transverse voltage can be reduced with suitable optics.
Slide7What the UK can provide
PDRA
The PDRA will be based at CERN for the duration of the project to from the design to the final commissioning of the TDC.
RF structure
We would provide the structure, but would require CERN to provide RF infrastructure (klystron, modulator,
etc
)
Slide8Points to consider for discussion
Spectrometer resolution
The TDC spreads outs the electrons over the screen
Do we need to upgrade the spectrometer to improve sensitivity and resolution?
Spatial constraints
The TDC will require a modulator, klystron, circulator,
etc
Is there space available nearby to accommodate all this equipment?
How much space is available upstream of the spectrometer dipole for the TDS?