Difference between revisions of "Beam Centering"
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[https://wiki.jlab.org/tegwiki/index.php/Installation_and_Commissioning <b>Back to Installation and Commissioning</b>] | [https://wiki.jlab.org/tegwiki/index.php/Installation_and_Commissioning <b>Back to Installation and Commissioning</b>] | ||
− | ==== Beam Centering procedure WITH | + | ==== Beam Centering procedure WITH spotL ==== |
<ol> | <ol> | ||
<li> Move target to None Target | <li> Move target to None Target | ||
<li> request 5uA beam with 2x2 raster | <li> request 5uA beam with 2x2 raster | ||
<ol type='a'> | <ol type='a'> | ||
− | <li> note scaler rates for s0, GC sum, & shower sum | + | <li> note scaler rates for s0, GC sum, & shower sum - take a scaler snapshot |
− | <li> Scaler rates with | + | <li> Scaler rates with cosmics |
[https://logbooks.jlab.org/entry/3489114 LHRS scalers] | [https://logbooks.jlab.org/entry/3489114 LHRS scalers] | ||
[https://logbooks.jlab.org/entry/3488877 RHRS scalers] | [https://logbooks.jlab.org/entry/3488877 RHRS scalers] | ||
Line 13: | Line 13: | ||
<li> Move target to Carbon Hole | <li> Move target to Carbon Hole | ||
<li> request 5uA beam with 2x2 raster | <li> request 5uA beam with 2x2 raster | ||
− | <li> Run CODA to take data, run | + | <li> Run CODA to take data, run spotL, look for hole on Tritium_run#.pdf |
− | <li> Compare spot ++ with | + | <li> Compare spot ++ with example [https://logbooks.jlab.org/entry/3464404 spotL Example] |
− | |||
− | |||
<ul> | <ul> | ||
− | <li> If: the square of the beam spot is visible, but the hole is not | + | <li> If: the square of the beam spot is visible, but the hole is not : [https://logbooks.jlab.org/files/2016/10/3432519/snapshot_1.png Example 2] |
<ol type='a'> <li> move the beam 2mm in any direction and return to step 4 </ol> | <ol type='a'> <li> move the beam 2mm in any direction and return to step 4 </ol> | ||
<li> Else If: the hole is visible in the square beam spot | <li> Else If: the hole is visible in the square beam spot | ||
− | <ol type='a'> <li> center the hole in the square by moving the beam | + | <ol type='a'> <li> center the hole in the square by moving the beam |
− | <li> [https://logbooks.jlab.org/ | + | <li> Should look like this [https://logbooks.jlab.org/entry/3504068 spotL] |
+ | </ol> | ||
<li> Else If: the beam spot doesn't look right | <li> Else If: the beam spot doesn't look right | ||
<ol type='a'> <li> Tell the Run Coordinator! | <ol type='a'> <li> Tell the Run Coordinator! | ||
− | <li> Proceed to "Coarse Beam Centering WITHOUT | + | <li> Proceed to "Coarse Beam Centering WITHOUT spotL" </ol> |
</ul> | </ul> | ||
<li> Proceed to "Raster Target Check" | <li> Proceed to "Raster Target Check" | ||
Line 31: | Line 30: | ||
</ol> | </ol> | ||
− | ==== Coarse Beam Centering procedure WITHOUT | + | ==== Coarse Beam Centering procedure WITHOUT spotL: ==== |
<span style="color:red"> CALL RC BEFORE EXECUTING THIS PROCEDURE. YOU SHOULD NORMALLY USE SPOT++ INSTEAD </span> | <span style="color:red"> CALL RC BEFORE EXECUTING THIS PROCEDURE. YOU SHOULD NORMALLY USE SPOT++ INSTEAD </span> | ||
<ol> | <ol> | ||
Line 45: | Line 44: | ||
<li> If 4a ~ 2a: | <li> If 4a ~ 2a: | ||
<ol type='a'> <li> Congratulations! The beam center is within 2mm of target center! | <ol type='a'> <li> Congratulations! The beam center is within 2mm of target center! | ||
− | <li> Proceed to "Fine Beam Centering WITHOUT | + | <li> Proceed to "Fine Beam Centering WITHOUT spotL" </ol> |
<li> Else If 4a > 2a: | <li> Else If 4a > 2a: | ||
<ol type='a'> <li> The beam is hitting the carbon | <ol type='a'> <li> The beam is hitting the carbon | ||
Line 59: | Line 58: | ||
<li> note beam position (x,y) </ol> | <li> note beam position (x,y) </ol> | ||
<li> use 5c(x,y), 7a(x,y), and 8c(x,y) to calculate the center of the circular carbon target | <li> use 5c(x,y), 7a(x,y), and 8c(x,y) to calculate the center of the circular carbon target | ||
− | <li> Proceed to "Fine Beam Centering WITHOUT | + | <li> Proceed to "Fine Beam Centering WITHOUT spotL" |
</ol> | </ol> | ||
− | ==== Fine Beam Centering WITHOUT | + | ==== Fine Beam Centering WITHOUT spotL: ==== |
− | <span style="color:red"> CALL RC BEFORE EXECUTING THIS PROCEDURE. YOU SHOULD NORMALLY USE | + | <span style="color:red"> CALL RC BEFORE EXECUTING THIS PROCEDURE. YOU SHOULD NORMALLY USE SPOTL INSTEAD </span> |
<ol> | <ol> | ||
<li> Request 5uA unrastered beam | <li> Request 5uA unrastered beam | ||
Line 77: | Line 76: | ||
==== Raster Target Check: ==== | ==== Raster Target Check: ==== | ||
<ol> | <ol> | ||
+ | <li> Move to Home | ||
+ | <li> Request 5uA, unrastered beam, note T1 scaler rate | ||
<li> Move to Raster Target | <li> Move to Raster Target | ||
− | <li> Request 5uA, unrastered beam, note scaler | + | <li> Request 5uA, unrastered beam, note T1 scaler rate |
− | <li> Request 5uA, 2x2 rastered beam, note scaler rates | + | <li> Request 5uA, 2x2 rastered beam, note T1 scaler rates |
− | <li> If | + | <li> If all three rates are similar and low (~few Hz), proceed with data taking |
− | <li> If the rastered rate is higher, repeat beam-centering procedure | + | <li> If the rastered rate is higher, call RC and repeat beam-centering procedure |
Latest revision as of 17:40, 16 December 2017
Back to Installation and Commissioning
Beam Centering procedure WITH spotL
- Move target to None Target
- request 5uA beam with 2x2 raster
- note scaler rates for s0, GC sum, & shower sum - take a scaler snapshot
- Scaler rates with cosmics LHRS scalers RHRS scalers
- Move target to Carbon Hole
- request 5uA beam with 2x2 raster
- Run CODA to take data, run spotL, look for hole on Tritium_run#.pdf
- Compare spot ++ with example spotL Example
- If: the square of the beam spot is visible, but the hole is not : Example 2
- move the beam 2mm in any direction and return to step 4
- Else If: the hole is visible in the square beam spot
- center the hole in the square by moving the beam
- Should look like this spotL
- Else If: the beam spot doesn't look right
- Tell the Run Coordinator!
- Proceed to "Coarse Beam Centering WITHOUT spotL"
- If: the square of the beam spot is visible, but the hole is not : Example 2
- Proceed to "Raster Target Check"
- When beam is centered, scaler rates should be similar to those in step 2b (cosmic rates)
Coarse Beam Centering procedure WITHOUT spotL:
CALL RC BEFORE EXECUTING THIS PROCEDURE. YOU SHOULD NORMALLY USE SPOT++ INSTEAD
- Move target to None Target
- Request pulsed, unrastered beam
- note scaler rates
- Move target to Carbon Single Foil
- note scaler rates (make sure rates are noticeably higher than Step 2a!)
- Move target to Carbon Hole
- Request delivery of pulsed, unrastered beam
- note scaler rates
- If 4a ~ 2a:
- Congratulations! The beam center is within 2mm of target center!
- Proceed to "Fine Beam Centering WITHOUT spotL"
- Else If 4a > 2a:
- The beam is hitting the carbon
- Scan the beam in +x direction until the beam hits the target support structure (scaler rates will get much larger).
- note beam position (x,y)
- move beam +/- 1mm in y, note scaler rates for each
- scan the beam in -x direction until the beam hits the target support structure
- note beam position (x,y)
- If Step 6 +y > -y:
- change beam x position to average of Step 5c x-position and Step 7a x-position
- scan beam in +y direction until the beam hits the target support structure
- note beam position (x,y)
- use 5c(x,y), 7a(x,y), and 8c(x,y) to calculate the center of the circular carbon target
- Proceed to "Fine Beam Centering WITHOUT spotL"
Fine Beam Centering WITHOUT spotL:
CALL RC BEFORE EXECUTING THIS PROCEDURE. YOU SHOULD NORMALLY USE SPOTL INSTEAD
- Request 5uA unrastered beam
- Find three points on the edge of the carbon hole, with a similar technique as in "Coarse Beam Centering"
- Calculate center of carbon hole using the three edge points.
- Move beam to calculated center position
- Proceed to "Raster Target Check"
Raster Target Check:
- Move to Home
- Request 5uA, unrastered beam, note T1 scaler rate
- Move to Raster Target
- Request 5uA, unrastered beam, note T1 scaler rate
- Request 5uA, 2x2 rastered beam, note T1 scaler rates
- If all three rates are similar and low (~few Hz), proceed with data taking
- If the rastered rate is higher, call RC and repeat beam-centering procedure