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Beamline

1. Beamline Target/Misalignment problem

2. Magnet measurements

3. Everything that’ critical and outstanding – eg d/str beamline monitors final use cases

- complete commissioning plan - apologies if this section is incomplete.

4. Beamline review – 16th.

Kevin Tilley MICE VC. 1st November

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1. Beamline / MICE-Target Misalignment

Seeds of a problem:-

At cm19: Observation that MICE target & beamline axis may not “necessarily” coincide. MICE target quoted as intercepting beam at ~+40mm above beam centre.

Subsequent to cm19: Beamline assumes target is & points back at +65mm above beam centre. MICE target at ~+40mm above beam centre.

-> beam starts at y=-25mm, y’=+9.7mrad. -> beam will misteer.

-> beam will pass through ISIS vacuum vessel.

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1. Beamline / MICE-Target Misalignment

What effect would the misalignment have, if true:-

i) Optical misalignment:-

- Before decay solenoid – central ray has y=0 y’=+20mrad. - pion flux is 20% down due to steering &

scraping- After TOF1:- - change in alignment of muon beam into

MICE (hence effect on max cooling

performance)

ii) Beam passage through vacuum vessel:-Scenario Flux at MICE

(arb units of

muons. Nmll +/-10% momentum cut)

Basic beam optics design:-65mm source, no steel:

5196

Current situation:-40mm source, 10mm sidewall

(at 25deg->23mm in direction of beam) 840

What we should have:-65mm source, 2mm window parallel to ISIS

(at 25deg->4.7mm in direction of beam) 2840

From 65mm point

From 40mm point

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1. Beamline / MICE-Target Misalignment

Corroborating the numbers:-

1) Axis of beamline:- 65mm from engineering (apologies for the diagram)

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1. Beamline / MICE-Target Misalignment

Corroborating the numbers:-

2) Target dip: 40mm?? - 3 approaches to corroborate:

Approach 1/3:-

Sheffield are checking their numbers which gave position at which target intercepted beam:

eg. 40mm? = physical offset in unpowered + (internal measure @ clip – internal @ unpowered)…. Underway.

physical offset in unpowered.

Internal measure @ unpowered

Internal measure @ clip

40mm?

- From diagrams.- Else whole thing from Laras computations

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1. Beamline / MICE-Target Misalignment

Corroborating the numbers:-

2) Target dip: 40mm? 3 Approaches to corroborate Approach 2/3:-

Measurements: target dipped at least 20mm from edge of beam when at 2ms. Beam within beampipe -> Thus dips from somewhere below 67mm -> somewhere below 47mm.

cf MICE 40mm measurement.

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1. Beamline / MICE-Target Misalignment

Corroborating the numbers:-

2) Target dip: 40mm? 3 Approaches to corroborate

Approach 3/3:- From the Old HEP target:

Target nominal centre position: 63.5mm.

Target size to tip ~ 6.25mm Target oscillation amplitude ~ 5mm ISIS Beam bumps ~ 15mm.

-> 63.5-6.25-5-15 = 40mm to centre of (bumped) beam. = cf 40mm MICE tgt

measurement This doesn’t take account different

positions of HEP target &MICE target (MICE target is ~760mm upstream. Difft

beamsizes – assume (bigger,less dense) -> same overall movement.

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1. Beamline / MICE-Target Misalignment

Proposal / solution.

Plan to realign beamline axis & vacuum vessel around 38mm datum.- Reason: -MICE target measurement actually 40-37mm. - We may wish to dip further in to increase rates. - Thus choose 38mm.

New vacuum vessel

New upstream frame with largertilt to aim at +38mm.

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2. Magnet measurements.

Plan to measure Q4-Q9 from next week hopefully onwards. ~ 1 x Q35 per week?

B2 from early December hopefully.

Recheck above polarities when hooked up (Dec/Jan)

Return to B1 when hooked up – late Jan (polarities)

Return to Q1-Q3 when hooked up – late Jan (polarities)

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3. Everything that’ critical and outstanding

– eg d/str monitors final use cases (TOF0/1 good enough?)

- complete commissioning plan

- apologies if this section is incomplete.

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4. Beamline Review

16th November.

Finish Agenda/charge & forward – discussion after VC? – OR TOMORROW PREFERABLY?

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Extra Slides:- Effect of passing through thick vacuum vessel.

Calculation of beam fraction traversing thick steel:-Assuming source at 40mm point above vacuum pipe centre:-centre relative to edge of window:- (40/2)-(65-40)+214 tan (9.7mr)~-3mm.Then beam overlap is: 3.75mm (beam half-height) -3mm -> overlap of ~ 0.75mm. Rest of beam height, 6.75mm tranverses thick steel. Note if beam drops to 38mm puts more in steel (comp a little by angle).Vessel same, quads aligned – removes angle – puts centre to -5mm. Hence all beam in steel.Thus at present, from source at 40mm, most of beam passes through the thick steel.

Impact on beam at MICE:-

Scenario Flux at MICE (arbitrary units of muons. Normal +/-10% momentum cut)

Beam optics design:-65mm source, no steel: 5196

Current situation:-40mm source, 10mm sidewall(at 25deg->23mm in direction of beam) 840

Possible changes:-40mm source, 2mm window prl to to ISIS (at 25deg->4.7mm in direction of beam) 2840 40mm source, 2mm wdw perp to MICE beam(perpendicular->2mm in direction of beam) 3773

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From 65mm point

From 40mm point

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Original design optic – no upstream steel.

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Current situation. Original design optic (red) & rms-profiles with 23mm stainless steel (below beam window & thru 10mm @ 25deg = 23mm).

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Possible change. 2mm window parallel to ISIS beam (as currently, but lowered).Original design optic (red) & rms-profiles with 4.7mm stainless steel (thru 2mm beam window @ 25deg = 4.7mm).

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Possible change. (2mm Beam window perpendicular to MICE beam: presenting 2mm only)