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Vacuum downstream the spectrometer
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Europe/Zurich
6/2-004 (CERN)
AWAKE Secondary Beamline Vacuum Meeting – 30/07/2025
Present: Arthur Clairembaud, Jose Antonio Ferreira Somoza, Edda Gschwendtner, Marlene Turner, Claudia Ahdida, Collette Pakuza, Benjamin Moser, Eduardo Granados
Goal of this meeting: discuss how to handle the vacuum downstream the second AWAKE plasma.
Dipole Spectrometer Vacuum Chamber
- The proton beam halo will interact with the currently selected dipole (80 mm aperture), leading to some activation.
- José suggested using a refurbished FTN dipole instead, which has a 100 mm aperture.
--> Action: Marlene to follow up with the Magnets team (Philip Schwarz and Daniele Schorling).
Beam Pipe Diameter Change Downstream of Spectrometer Dipole
- First model of the spectrometer dipole chamber proposed by Nicolas Chritin
- The chamber design could be modified to allow a faster aperture opening.
--> Action: José to discuss possible design options with Nicolas.
- Laser Merging Mirror needs a 100 mm diameter chamber
- Part of the proton beam halo may interact with the mirror mount; this should not pose a problem.
--> Action: Edu to decide on the mirror aperture and confirm there are no issues with motorization (e.g., halo intercepting motors).
Options
1) Containment of the entire beam in vacuum: Keep the entire proton beam within ~300 mm diameter round pipes (~3 m sections), increasing in size along the beamline and offset relative to the proton beam trajectory.
2) Propagation in Air: Propagate the proton beam in air after the laser merging mirror and streak camera screen. This option requires additional vacuum windows.
How to decide:
1) Work on the screen(s) design: Determine the number of screens required (which will define the number of additional vacuum windows).
--> Action: Marlene and Arthur to organize a dedicated meeting.
2) Then decide whether to propagation in air or vacuum makes more sense.
3) Then incorporate design consequences into the R2E simulations.
--> Action: Marlene and Claudia to follow up.
Note from Jose per email on 1st of August:
In order to use standard pipes, where designs and spares are already available in stock (some of the tube has to be produced), the pipes to use after the spectrometer (if it finally requires vacuum) are (inner diameter) 155.8 mm, 215.1 mm and 267.8 mm. The larger is not far of the 300 mm required. Larger sizes are also possible, but we have a preference for those diameters as they are SPS standards (that correspond to DN 159, 219 and 273).
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