OMEGA 60

CHAMBER/TARGETRY

• Beam layout image

• Chamber pressure ~1e-5 to 1e-6 Torr

• One degree of rotational freedom on targets

• Only backlit alignment

• Coordinates:

  • Theta: declination from straight up (0 deg = up) range 0 to 180 (no negative)

  • Phi: (0-360deg) 

  • zero ~ North

  • Increases anti-clockwise

• Need to be V careful with maintain up-to-date target 'drawings' ESPECIALLY any changes during manufacture

SHOT CYCLE

• 45 minutes between shots (minimum)

• Morning 4.5 hrs, afternoon 6.5 hrs

• Typically the shot-cyle is slower before lunch:

  • Test things before lunch giving time to evaluate before shooting really begins in afternoon

• Alternate subsequent shots between those relying on different diagnostics

LASER CHARACTERISTICS

• 1st shot of day is least perfect

• Debris shield replaced every 3 weeks (prior to cryo-shots)

• Pointing from TCC:

  • +/-5mm in vertical

  • -9mm +15mm in horizontal

• f/# 6.7

PULSE SHAPING/BEAM TIMINGS

• Pulse shapes must be requested at least 1 month in advance. See here

• All beams timed as if they are to TCC - must account for this!

• Can offset individual beams by up to ~+/-5ns on a per shot basis, but see here for exact details for each beam:

  • PLAS (Path Length Adjustment System)

  • Adjusting beam timings between shots doesn't incur a delay

• Pulse shapes 100ps → 4ns

• Up to 2 pulse shapes per shot, but the way this is mapped from legs to beams is highly restrictive (see beam numbering below) 

• Pheonix regen means can have no SSD late in time so more energy

• Backlighter can be done separately at A split (1 → 3 beams) and can have big offset in time

BEAM LAYOUT/NUMBERING

• 23, 48, 62 degree and equatorial cones in both north and south poles

• Like a football: pentagons and hexagons

• Beam numbering system:

  • Leg 1: clusters 1 and 4

  • Leg 2: clusters 2 and 5

  • Leg 3: clusters 3 and 6

  • numbering works by cluster|number, e.g. 62 is cluster 6, beam 2

• Each beam is directly opposed by another

  • Must be careful target is not completely ablated

ENERGETICS

• With SSD: 

  • 27kJ | 450J/beam (1ns square pulse)

  • ~27TW total power

  • 0.45TW/beam

• No SSD: 

  • 500J/beam

  • 0.5TW/beam

• The details of the pulse shape always dictates energy and peak power, so cannot assume anything until this is set​

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PHASE PLATES

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EXPERIMENTAL TIMELINE

Brief timeline for an Omega experiment:

• »3 months out

  • Finalize target design and submit request. Typically in April/May

• ~4 months out

  • Submit experimental proposal with all unique configurations described (SRF and VisRad model required for each) and all diagnostics intended to be used

• >2 months

  • Proposal approved by Facility Advisory and Scheduling Committee (FASC)

• COB Monday 2 weeks prior to experimental shot date

  • Unique SRFs complete for review at 2-week PI brief (typically conducted on Wednesday afternoon 2 weeks prior to experimental shot date)

• COB Monday 1 week prior to experimental shot date

  • SRF for all planned shots completed for review at 1-week PI brief (typically conducted on Wednesday afternoon 1 week prior to experimental shot date)

• Monday of shot week

  • Brief presentation at LLE's experimental meeting

• Day of shots

  • Arrive 7.30am (with doughtnuts, bagels and coffee)

  • 8am Brief presentation to watch crew at pre-watch brief

DIAGNOSTICS

Click above link to see diagnostics information.