Measurement of transverse
emittances with a Solenoid
(for GUN-0.1)
- Jens Völker –
(06.12.2011)
Summary
Technics and analysis for a Solenoid-Scan
- Theory of a Solenoid-Scan
- Simulation of the Solenoid
Measurements
Discussion
Emittance measurement
with a solenoid-scan
(Jens Völker) 06.12.2011
Emittancemeasurement
with a solenoid-scan
(Jens Völker)
Technics for a Solenoid-Scan
Schematic construction of the test facility
SRF-Gun
Solenoid
BendingMagnet
YAG-screen
(150µm thick)
Pb-Cathode
Drive-Laser
(λ=258nm)
Faraday-Cup /
dump
Emittance measurement
a solenoid-scan
Völker) 06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
Theory of a Solenoid-Scan
transverse beam width (rms) on screen:
β-function determined by Twiss-Matrix
L = Solenoid to Screen
Leff = effective length of the Solenoid
Emittance measurement
a solenoid-scan
Völker)
06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
- SolenoidScan
Theory of a Solenoid-Scan
transverse beam width (rms) on screen:
β-function determined by Twiss-Matrix
φ<1 => expansion to first order
Emittance measurement
a solenoid-scan
Völker)
06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
- SolenoidScan
Theory of a Solenoid-Scan
transverse beam width (rms) on screen:
β-function determined by Twiss-Matrix
Emittance measurement
a solenoid-scan
Völker)
06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
- SolenoidScan
Theory of a Solenoid-Scan
transverse beam width (rms) on screen:
β-function determined by Twiss-Matrix
?
?
will be determined by simulations
Emittance measurement
a solenoid-scan
Völker)
06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
- SolenoidScan
Simulation of the Solenoid
1. step:
calculations of the B-field in the
Solenoid
by Poisson-Superfish:
Coil-pack
Iron-yoke
Cu-cooling
µ-Shield
Beam-pipe
Emittance measurement
with a solenoid-scan
(Jens– Völker)
06.12.2011
Emittancemeasurement
with a solenoid-scan
(Jens Völker)
Solenoid-Simulations
Simulation of the Solenoid
1. step:
2. step:
3. step:
calculations of the B-field in the
Solenoid
by Poisson-Superfish:
Integrate the 3d-fields
into ASTRA
determine the transfer-matrix by
special particle-distributions
(parallel-particle-beam and
particle-spotlights)
Emittance measurement
with a solenoid-scan
(Jens– Völker)
06.12.2011
Emittancemeasurement
with a solenoid-scan
(Jens Völker)
Solenoid-Simulations
Simulation of the Solenoid
Fit-solutions:
Emittance measurement
with a solenoid-scan
(Jens– Völker)
06.12.2011
Emittancemeasurement
with a solenoid-scan
(Jens Völker)
Solenoid-Simulations
Analysis by using an example
not emittance
conserving
Emittance measurement
a solenoid-scan
Völker)
06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
- Example
Analysis by using an example
Simulations of Soleonoid-Scans by ASTRA
Emittances increase behind the
focus-point!
min. bunch-width on Screen
Emittance measurement
a solenoid-scan
Völker)
06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
- Example
Analysis by using an example
high-cut
not emittance
conserving
Emittance measurement
a solenoid-scan
Völker)
06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
- Example
x‘ (mm/m)
y‘ (mm/m)
Analysis by using an example
x (mm)
y (mm)
Emittance measurement
a solenoid-scan
Völker)
06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
- Example
Measurements
roughness of the
cathode surface
Theory:
higher order effects:
- aberrations
- displacements
- asymmetries
bunch
charges
All terms are generally correlated of each other and also
depends on other effects (e.g. Shottky-effects)
Emittance measurement
a solenoid-scan
Völker)
06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
- Emittance
Measurements
emittances depends on :
• Laser spot size
• gradient of the electric field in Cavity
and extraction phase of the bunch
• Laser intensity
Emittance measurement
a solenoid-scan
Völker) 06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
Measurements
Emittance measurement
a solenoid-scan
Völker) 06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
Measurements
Emittance measurement
a solenoid-scan
Völker) 06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
Measurements
εx
εy
Emittance measurement
a solenoid-scan
Völker) 06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
Discussion
What are the effects that dominate the emittance values?
Emittance growth
Uncertainties in Measurements
by cathode surface
Displacement of cavity and solenoid axis
Beam misalignment
Asymetries of the E- or B-fields
electronscattering in thick screen
Emittance measurement
a solenoid-scan
Völker) 06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
Discussion
What are the effects that dominate the emittance values?
Emittance growth
Uncertainties in Measurements
by cathode surface
Displacement of cavity and solenoid axis
Beam misalignment
Asymetries of the E- or B-fields
electronscattering in thick screen
for the next run:
- Solenoid will be movable in the transvers space
Emittance measurement
a solenoid-scan
Völker) 06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
Discussion
What are the effects that dominate the emittance values?
Emittance growth
Uncertainties in Measurements
by cathode surface
Displacement of cavity and solenoid axis
Beam misalignment
Asymetries of the E- or B-fields
electronscattering in thick screen
for the next run:
- Solenoid will be movable in the transverse space
- a small quadrupol will be installed behind the Solenoid
Emittance measurement
a solenoid-scan
Völker) 06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
Discussion
What are the effects that dominate the emittance values?
Emittance growth
Uncertainties in measurements
by cathode surface
Displacement of cavity and solenoid axis
Beam misalignment
Asymetries of the E- or B-fields
electronscattering in thick screen
for the next run:
- Solenoid will be movable in the transverse space
- a small quadrupol will be installed behind the Solenoid
- new screen-station (4 screens) with varying thickness an
material + a wire-scanner
Emittance measurement
a solenoid-scan
Völker) 06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
Discussion
What are the effects that dominate the emittance values?
Emittance growth
Uncertainties in measurements
by cathode surface
Displacement of cavity and solenoid axis
Beam misalignment
Asymetries of the E- or B-fields
electronscattering in thick screen
for the next run:
- Solenoid will be movable in the transverse space
- a small quadrupol will be installed behind the Solenoid
- new screen-station (4 screens) with varying thickness an
material + a wire-scanner
- new methode for the measurement: slit-mask
Emittance measurement
a solenoid-scan
Völker) 06.12.2011
Emittancemeasurement
with awith
solenoid-scan
(Jens(Jens
Völker)
Thank you for
your attention.
Extras
Emittance measurement with a solenoid-scan (Jens Völker) 06.12.2011
Extras
Emittance measurement with a solenoid-scan (Jens Völker) 06.12.2011