Awake electron beamrequirements

Parameter Baseline Phase 2 Range to check

Beam Energy 16 MeV 10- 20 MeV

Energy spread (s) 0.5 % < 0.5 % ?

Bunch Length (s) 4 ps 0.3-10 ps

Beam Focus Size (s) 250 mm 0.25 – 1mm

Normalized Emittance (rms) 2 mm mmrad 0.5 - 5 mm mrad

Bunch Charge 0.2 nC 0.1 - 1 nC

Let’s assume gaussian or truncated gaussian distributions for transverse phase space for time beingFor the longitudinal we will simulate gaussian and somewhat more uniform distribution depending what we can expect from the laser

No changes

Specifications for AWAKE photo-injectorBaseline (9,4 ps) 10 ps 0.3 ps Unit

e- beam Charge / bunch 0.2 1.0 0.1 nCBunch population 1.25E+09 6.25E+09 6.25E+08Bunch width (s) 4.000 4.255 0.128 psBunch width (FWHM) 9.40 10 0.30 psBunch length 0.282 0.3 0.009 cmNormalized emittance 2 2 2 p.mm.mradCathode material Cu Cu Cu

Photo-cathodeQuantum Efficiency 0.003 0.003 0.003 %Wavelength 262 262 262 nmUV energy / bunch @ the cathode 32 158 16 mJUV energy / bunch @ laser lab 90 451 45 mJ

Laser beam conv. and transport Transport of UV from laser to e-gun 0.5 0.5 0.5

Transport of UV to cathode 0.7 0.7 0.7

Effeicency of pulse compressor 0.6 0.6 0.6IR-UV conversion efficiency 0.1 0.1 0.1Efficiency of UV stretcher 0.5 0.5 1Beam shaping 0.8 0.8 0.8Safe margin 0.7 0.7 0.7UV cath. energy / Output IR energy 0.006 0.006 0.012IR pulse energy required 5366 26830 1342 mJ

Ablation limits

Litearture Ablation treshold from literature (Hashida 2002) 18 18 18 mJ/cm2data ref. pulse duration 0.07 0.07 0.07 ps

ref. wavelength 800 800 800 nmcorrection for UV 0.7 0.7 0.7

Estimation of the limit correction for pulse duration 26.2 27.3 2.6

Estimated ablation threshold 330 344 33 mJ/cm2Laser beam radius (waist) @ the cathode 0.9 2 2 mm

Safe size Peak laser fluence (gaussian beam) 248 251 25 mJ/cm2estimation Ratio to ablation threshold 0.75 0.73 0.76

Laser requirements

50 mJ

500 mJ

Laser update We still assume using  copper cathodes Prefer a solution where Amplitude delivers a UV laser beam

This means they take care of the compression and the 3rd harmonic generation. CERN would then transport the UV to the gun and cathode. UV pulse required:

Wavelength: 262 nm; 500 uJ pulse energy and a FWHM pulse length of 10 ps.This pulse would guarantee the base line parameters and the 1 nC option.

For the short pulse 0.3 ps we would need  only 50 uJ in the UV assuming that we would have to produce only 0.1 nC of charge (limited by ablation)

Pulse compression independent from the one for the proton beam Independent pulse picker allowing to use only some pulses out of the 10 Hz rep. rate.

The specification for an IR beam would be a pulse energy of 50 mJ.

We will still try to investigate the space constraints and keep the option to use different cathodes.

Electron source layout

Electron source layout

Laser table needs to be integrated as well

Electron source layout

Comments:

Layout is advancingSome conflicts with the overall

lengthNeed to optimise cathode

accelerating structure distanceNeed to specify quadrupolesStudy cathode loading system

optionsStudy shielding design and layout

Electron source design

Oznur Mete, Cockcroft

Starting points for calculations Proton line: the top mirror in vacuum before the laser core

tunnel

Electron line: intersection of the “electron” laser beam with the vertical plane formed by 2 vacuum mirrors for “proton” beam

727

98

Valentine and Mikhail

7387320

1188vertica

l 19929

7387+1188+320+19929 = 28824 mm Proton line: path to plasma cell

Electron line: path to photocathode

9846

1087vertical

1320

500 817

Optical table 1000x1800

9846+1087+1320+500+817 = 13570 mm

Electron beam path from photocathode to plasma cell

4627

377

377

377

377

3683

736

1536

4319

4627+377*4+3683+736+1536+4319 = 16409 mm

Summary Proton line path to plasma cell = 28824 mm• Electron line: laser path + electron path = 29979 mm

difference = - 1155 mm is to be compensated by delaying the “proton” pulse (could it exist in the main amplifier ?)

Delays due to compressor, THG, UV stretcher, telescope, are not counted!

A variable delay of 0 - 200 mm in the electron line is required