measurement of transverse emittances with a solenoid (for gun-0.1) - jens völker – (06.12.2011)

Measurement of transverse emittances with a Solenoid

(for GUN-0.1)

- Jens Völker –(06.12.2011)

Technics and analysis for a Solenoid-Scan- Theory of a Solenoid-Scan- Simulation of the Solenoid

Measurements

Discussion

Emittancemeasurement with a solenoid-scan (Jens Völker)

Summary

Emittance measurement with a solenoid-scan (Jens Völker) 06.12.2011

SRF-GunSolenoid

Drive-Laser(λ=258nm) Pb-Cathode

Faraday-Cup / dump

YAG-screen(150µm thick)

Bending-Magnet

Schematic construction of the test facility


Technics for a Solenoid-Scan


transverse beam width (rms) on screen:

β-function determined by Twiss-Matrix

L = Solenoid to ScreenLeff = effective length of the Solenoid

Emittancemeasurement with a solenoid-scan (Jens Völker) - SolenoidScan

Theory of a Solenoid-Scan




φ<1 => expansion to first order






?

?

will be determined by simulations




1. step: calculations of the B-field in the Solenoidby Poisson-Superfish:

Beam-pipe

Coil-pack

Iron-yoke

Cu-cooling

µ-Shield

Emittancemeasurement with a solenoid-scan (Jens Völker) – Solenoid-Simulations

Simulation of the Solenoid


2. step: Integrate the 3d-fields into ASTRA

3. step: determine the transfer-matrix by special particle-distributions(parallel-particle-beam and particle-spotlights)

1. step: calculations of the B-field in the Solenoidby Poisson-Superfish:




Fit-solutions:




not emittance conserving

Emittancemeasurement with a solenoid-scan (Jens Völker) - Example

Analysis by using an example


Simulations of Soleonoid-Scans by ASTRA

min. bunch-width on Screen

Emittances increase behind the focus-point!




not emittance conservinghigh-cut




x (mm) y (mm)

x‘ (

mm

/m)

y‘ (

mm

/m)




roughness of the cathode surface

bunch chargeshigher order effects:

- aberrations - displacements - asymmetries

All terms are generally correlated of each other and also depends on other effects (e.g. Shottky-effects)

Theory:

Emittancemeasurement with a solenoid-scan (Jens Völker) - Emittance

Measurements


emittances depends on :

• Laser spot size

• Laser intensity

• gradient of the electric field in Cavity and extraction phase of the bunch


Measurements



Measurements



Measurements

εy

εx


What are the effects that dominate the emittance values?

by cathode surface Displacement of cavity and solenoid axis

Beam misalignment Asymetries of the E- or B-fields

electronscattering in thick screen


Discussion

Emittance growth Uncertainties in Measurements



- Solenoid will be movable in the transvers space

for the next run:


Discussion







- Solenoid will be movable in the transverse space

- a small quadrupol will be installed behind the Solenoid

for the next run:


Discussion









for the next run:

- new screen-station (4 screens) with varying thickness an material + a wire-scanner


Discussion




Emittance growth Uncertainties in measurements





for the next run:

- new screen-station (4 screens) with varying thickness an material + a wire-scanner

- new methode for the measurement: slit-mask


Discussion




Emittance growth Uncertainties in measurements


Thank you for your attention.

Extras


measurement of transverse emittances with a solenoid (for gun-0.1) - jens völker – (06.12.2011)

Documents

solenoid emittancemeasurement

solenoid emittance measurement

example emittance measurement

srfgun solenoid drivelaser

shield emittancemeasurement

order emittancemeasurement

transverse beam width

screen emittances