AWAKE Electron Spectrometer Simon Jolly 7 th March 2013

Spectrometer Specifications Wakefield accelerated electrons ejected collinear with proton beam: need to separate the 2 and measure energy of electron beam only. Must be able to resolve energy spread as well as energy: spectrometer must accept a range of energies, probably 0-5 GeV. Current conceptual layout: –Dipole mounted ~2 m downstream of plasma exit induces dispersion in electron beam. –Scintillator screen 1 m downstream of dipole intercepts electron beam ONLY. –Dispersion gives energy-dependent position spread on screen. –Scintillator imaged by intensified CCD camera viewing upstream face of scintillator screen. 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting2

Spectrometer Layout (Isometric View) 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting3 Camera Scintillator Screen CERN 1 m dipole Plasma cell Protons Electrons + Protons Edge of scintillator screen is aligned with dipole coils (position will depend on resolution). Screen mounted at 45 degrees to beam axis. Camera is 4 m from centre of screen, mounted at 90 degrees to beam axis. Camera shown in horizontal bending plane. Camera can also be mounted vertically, directly above screen, with screen tilted at 45 degrees to vertical as well as 45 degrees to beam axis. Dipole to screen distance remains unchanged (independent of screen-camera orientation).

Spectrometer Layout (Plan View) 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting4 Electrons + Protons Protons Electrons CERN 1 m MBPS dipole Scintillato r Screen Camera For left-hand bend, beam enters at right-hand edge of dipole. Protons essentially unaffected; electrons bent in dipole field. Screen mounted at 45 degrees to beam axis. Camera is 4 m from centre of screen, mounted at 90 degrees to beam axis. 4 m 1.6 m 1 m

Spectrometer: Vacuum Vessel 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting5 Electrons + Protons Camera Screen mounted inside vacuum vessel, but camera outside. Light tight path from vacuum window to camera: doesn’t need to be permanent, just light tight… Vacuum Window Vacuu m Vessel Light Tight Path

Spectrometer: Shielding 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting6 Electrons + Protons Most important item to shield is CCD Camera. Needs to be as far from beamline as possible (while still close enough to receive enough light). Maximise distance to beam axis. More shielding required on upstream side. Vacuu m Vessel Shieldin g

CERN 1 m Dipole (Edda, Alexey) 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting7

Spectrometer Simulations Initial simulations of Spectrometer layout carried out by Alexey: –Effects of upstream quadrupole doublet. –Quick check of fringe field effects. More detailed simulations by Dan Hall (UCL) including Spectrometer GUI for checking spectrometer layout parameters quickly. GPT simulations using beam parameters from K. Lotov (good and bad…) for design setup, with and without fringe fields. 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting8

Spectrometer GUI: Assumptions 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting9 GUI and movies courtesy of Dan Hall (but don’t tell him…).

Good (“2 GeV”)Bad (“650 MeV”) Electron Beam Distributions 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting10

2 GeV, 1.86T: Trajectories 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting11

2 GeV, 1.86T: Screen 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting12

2 GeV, 1.86T: Screen (Zoom) 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting13

2 GeV, 1.86T: Spectrometer Energies 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting14

2 GeV, 1.86T: Energy Correlation 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting15

2 GeV, 1.86T: Energy Correlation (2) 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting16

2 GeV, 1.86T: Energy Resolution 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting17

650 MeV, 1T: Screen 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting18

650 MeV, 1.4T: Screen 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting19

650 MeV, 1.86T: Screen 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting20

650 MeV, 1T: Spectrometer Energies 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting21

650 MeV, 1.4T: Spectrometer Energies 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting22

650 MeV, 1.86T: Spectrometer Energies 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting23

650 MeV, 1.86T: With Fringe Fields 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting24

2 GeV, 1.86T: With Fringe Fields 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting25

2 GeV, 1.86T: Spectrometer Energies 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting26

Conclusions Fundamental design hasn’t changed: it’s still simple! Already have camera (but not lens) and magnet (but not power supply). Some nice simulation results from Dan Hall using Konstantin Lotov’s beams: –Preliminary results show we can resolve the energy distribution reasonably well. –With Konstantin’s parameters, energy spectrum not washed out by emittance. –Fringe fields start to affect large angle beams at low energy + high fields, but otherwise okay. –A note of caution: These are “idealised” fringe fields. May have nonlinearities/nonuniformities in actual magnet field. Definitely need magnetic field mapping + magnet “ramp” (hysteresis + power supply). Onwards to finding a scintillator… 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting27

CDR/Technical Note Status Matt Wing looking after spectrometer text/figures for CDR: –Text written. –Will include 1 or 2 plots I’ve just shown you. Technical note is somewhere between “draft” and “almost” done: –Have received corrections from Matt Wing and Patric Muggli on Design + Layout sections. –Simulations/Energy Reconstruction mostly plots: you’ve just seen them all… 07/03/13Simon Jolly, UCL, AWAKE Collaboration Meeting28