Injector Expert Procedures

Steering 100 kV region - Steigerwald Steer
Steering 100 kV region - spot move/Wein spin change
Prebuncher Phasing
Chopper Centering Procedure
Chopper 1 RF setup procedure
Chopper 2 RF setup Procedure
Buncher Centering
Buncher Phase/Amplitude Setup
Capture Phase/Amplitude Setup
Capture Centering
A3/A4 Centering
1/4 cryo Centering
Cresting the 1/4 cryo cavity
5 MeV region Setup
Chicane Setup Procedure
QE Scan
QE Measurement?

Steigerwald Steer

Steigerwald Steer is used to steer in an orbit in the 100 kV section of the machine after major reconfigurations or for initial setup of a gun. It suggests which correctors should be used to center the beam on corresponding viewers. THIS PROCEDURE SHOULD NOT BE USED FOR SPOT MOVES OR WIEN SPIN CHANGES - instead use the 100 kV allowed steering correctors.

The first viewer, ITV2I05 or ITV3I05, are typically not useful in that they often block the laser beam.

To do the initial steering of the front end of the machine, use the following correctors to center the beam as well as possible on the corresponding viewers - each correction will change the position of the beam on all the viewers, so if large corrections are necessary, it may be helpful to make them in small steps to avoid completely losing beam on other viewers.

· use MBH2I04 to center on 1I02

· use MBH2I05 to center on 1I03

· use MBH1I03 to center on 1I04

· use MBH1I04 to center on viewer 1I07

· use MBH1I06 to center on viewer 0I01A

· steer with MBH0I01A for A1 interception

· steer with MHD0I01 for A2 interception (magnet sits on A1)

100 kV steering Allowed correctors

For steering after a spot move or a spin change, there is a 100 kV steering script which should allow easy, automated orbit compensation in the 100 kV region of the injector. The steering script can be found on the MEDM window under the injector scripts. The script asks the user to zero the relative BPMs while the system is in a good state then moves the Wien or spot and uses the following correctors to get the BPMs back to zero. If the script is not working well, this can be done manually by adjusting the following allowed correctors.

The allowed 100 kV region corrector magnets are:
MHB1I03H/V    (Immediately before the Wien filter)
MWF1I04         (Wien BDL)
MBH1I04H/V    (Immediately after the Wien)
MBH1I06 H/V   (After the Wien)

MWF1I04 is only used in Spin change steering, but all other correctors can be used either for spin changes or for spot moves.

The help menu for this script can be found here.

Prebuncher Phasing

Bad Prebuncher phasing can cause problems with Master Slit interception. Bad prebuncher amplitude can result in large tails (to large) or large Master Slit interception (prebuncher amplitude to small). It is also possible that large A3 interception (after A1/A2 have been changed to 3 mm/6 mm holes) can be caused by running the prebuncher to hard. The other probable cause of high Master Slit interception in a well set-up machine is laser phase.

Prerequisites:

a. Steered through to chopper

b. Interception on A1/A2 minimized through using Steigerwald steering or Allowed correctors

c. Laser RF must be on

Procedure:

1. Establish tune mode beam through Faraday Cup 1 (at least – FC2 if possible)

2. Adjust steering with allowed correctors to again minimize interception on apertures A1 and A2

3. Turn on prebuncher to normal operating levels (normally 20-24 dBm)

4. Adjust prebuncher phase to minimize interception on the Master Slit. This will need to be done iteratively with steering to keep A1, A2 and A3 interception minimal.

Laser Phase Setup - Rough

Poor laser phase can cause large Master Slit interception. Laser phase can be roughly adjusted using the viewer ITV0I04 inside the chopper, or can be fine tuned by watching Master Slit interception as smaller changes in the phase are made. Rough adjustment is described first, with the procedure for fine adjustments following.

Prerequisites:

a. Chopper RF on

b. Viewer limited beam on (as many lasers on as will be needed)

c. Master Slit, Central plug and all chopping apertures retracted

d. Viewer ITV0I04 inserted

e. Prebuncher off

Procedure:

1. The goal of this rough adjustment procedure is to get the lasers going through the proper slits. The hall B laser should be going through the top slit always, and the A and C lasers through the slits at 4 and 8 o’clock. (Which goes through which slit has been varying recently).

2. Adjust the gang phase of the three lasers (steps of 20-30 degrees can be used if needed) to try to get the spots in the proper places. Turning off lasers so that only one is visible can help in identifying which spot corresponds to which laser. This gang phase change will change the phase of all three lasers, but not evenly. Wait a few seconds for the phases to settle after each adjustment.

3. The individual laser phase should in the range from +/- 40 degrees. If the individual laser phases are to far from zero, the laser RF is set up poorly and the gang phase needs to be moved again. After adjusting the gang phase, adjust each individual phase to get the spots closer to their proper positions. If this makes the individual phases move far from zero, back out and readjust the gang phase before trying to adjust the individual phases.

4. Repeat gang phase moves and individual laser phase moves until the spots are in roughly the proper locations to travel through their slits and individual laser phases are not to far from zero.

5. Proceed to fine tuning of laser phase (procedure below).

Laser Phase Setup – Fine Tuning

Use the following procedure if only fine tuning of the laser phase is needed rather than the initial setup of the system, or to finish optimization after a rough setup of the laser phase.

Prerequisites:

a. Laser phases are approximately correct (each hall’s beam is going through the correct slit)

b. Tune mode beam to at least FC#1.

c. Slits are should be in approximately the position where they will be for beam delivery to the halls

Procedure:

1. Turn off the prebuncher

2. Turn on tune mode beam for either an individual hall or all three halls. (All three makes it more difficult to determine which one to move when, but eliminates the need for repeating for each then trying to reconcile the different settings)

3. Look at the interceptions on Master Slit and aperatures A1 and A2

4. Adjust the gang phase of the 3 laser RF phase – steps of 2-3 degrees are appropriate at this point. This will adjust the phase of each laser, but not equally. Wait a few seconds for the laser RF phases to settle. If this helped, proceed to step 5. If not, try adjusting gang phase in the other direction.

5. Adjust the phase of the individual laser RF by a few degrees, keeping the individual laser RF phase near zero (do not exceed +/- 40 degrees).

6. Repeat steps 2-5 for each hall, trying not to move the gang phase much. Ideally you will find one gang phase and three individual laser phases where the individual phases are all near zero and the Master Slit interception is minimized.

Chopper Centering Procedure

The chopper will need to be centered after large orbit changes upstream, or as a routine part of a full optimization of the injector.

Prerequisites :

a. Viewer limited and tune mode beam will be used

b. Faraday cup 2 in

c. Buncher OFF

d. Chopper 1 and Chopper 2 RF OFF

e. All slits retracted

f. Master slit and Central Plug withdrawn

g. This can be done with the Laser RF off so that one laser will provide DC beam

Procedure:

First center beam on lens MFA0I03.

1. Verify that lens MFA0I03 is set to 1210 mA. This images A2 to the chopper viewer and the master slit.

2. Insert viewer ITV0I03 and turn on viewer limited beam.

3. Take MFA0I03 off loop, and swing its value to the limits, both positive and negative. If beam is centered on the lens, changing the lens value should focus and defocus the beam, but not steer it at all. If this is the case, return MFA0I03 to its setting of 1210 mA and proceed to step 7. Otherwise, continue with step 4.

4. Steer with MBH0I03H, and then repeat step 3. See if motion is lessened or worsened, and readjust MBH0I03 accordingly. Iterate until motion in this direction is minimal.

5. Steer with MBH0I03V, then repeat step 3. Iterate until motion is minimized.

6. Return MFA0I03 to its original setpoint of 1210 mA.

Next center the beam on the master slit. ("Tiny Spot")

7. Center the beam on the viewer ITV0I04 as best as possible

8. Insert the Master Slit, and setup to monitor current intercepted on Master Slit (oscillioscope can be used for this purpose)

9. Establish Tune Mode beam. It will most likely intercept the master slit

10. Steer with magnet MBH0I03 until Master Slit interception is minimized

11.

12. Insert viewer ITV0I05 and turn on viewer limited beam

13. A tiny spot should be visible on ITV0I05, indicating that beam is passing through the small center hole in the master slit. Use MBH0I03 to steer beam onto ITV0I05 into a small, centered spot.

14. Remove Master Slit.

Optional step: Center beam on MFD0I04

If desired, center the beam on MFD0I04, repeating the procedure in steps 1-6 but cycling MFD0I04 and steering with MBH0I03H/V. Ensure that this does not change the steering through the hole in the Master slit by reinserting the Master Slit and looking again with ITV0I05.

Next center the beam on lens MFA0I05

15. Center the beam on MFA0I05 by repeating steps 1-6, but looking at the beam on viewer ITV0I05 and steering with MBH0I04.

Proceed to Chopper RF setup

Chopper 1 RF setup

Chopper 1 RF setup will be needed after major rework of the optics of the injector, or after replacement of RF system parts. Any time chopper 1 RF setup is performed, chopper 2 RF must also be performed.

Prerequisites:

a. Beam centered in choppers (see chopper centering procedure)

b. Viewer limited mode beam

c. Faraday Cup #1 (IFY0I06) inserted

Procedure:

1. Set the Chopper 1X and 1Y gradients:

a. Turn on chopper 1X and allow about 1 minute for RF to settle. Insert viewer ITV0I04 (removing master slit and central plug first - controls can be found on top right of injector viewer screen) and measure the length of the line on the viewer. It is normally about 1.75 inches on the screen, corresponding to a size in the chopper of approximately 3 cm. Only major variations from the nominal measurement need be altered.

b. Turn off chopper 1X and turn on chopper 1Y. Again set the line length to 1.75 inches on the screen.

2. Set the Chopper 1X and 1Y phases

a. Turn on chopper 1X and 1Y and wait for a few seconds for phases to lock.

b. Set phase of chopper 1X to zero. Old instructions: Set chopper 1 and chopper 2 gang phase to zero.

c. Adjust chopper 1Y phase until the ellipse on viewer 0I04 collapses to a straight line at +/- 45 degrees.

d. Add 90 degrees to chopper 1Y. There should be a circle of radius 1.75 inches on the screen.

3. Verify size and aspect ratio of the beam circle by taking a picture of the screen with the DATACUBE program and using its analysis features.

Chopper 2 RF setup

Prerequisites:

a. Chopper 1 RF setup properly following procedure.

b. Chopper 1X and 1Y RF on.

c. Chopper 2X and 2Y RF on.

d. Start with approximately correct values of the chopper 2X and 2Y gradients. If you need a starting value, use the chopper 1X and 1Y values for the starting point.

Setup:

1. Record current setpoints of the following lenses:
MFA0I05:_______ (nominally 982 mA) MFA0I06:________ (nominally 1200 mA)

2. Make sure viewer 0I04 is retracted and insert master slit and central plug (controls can be found on top right of injector viewer screen)

3. This procedure can be performed either with the laser RF on or off:

a. With DC lasers (3 laser RF off):

i. Turn up diode laser seed level to a value noted somewhere in injector expert pages. This will need to be turned back down before the laser RF is turned back on!!!

ii. Retract slits to fully open (-1 mm).

b. With 3LaserRF on:

i. Move all slits to position of 25 mm (to reduce spots to small points)

ii. Turn on all three lasers

Procedure:

4. Insert viewer ITV0I05 and look for the beam. You will hopefully see either 1 spot or 3 spots. If you see 1 spot, the dechopping may be good. Good dechopping can be verified by first noting the gang phase of chopper 2 then rolling the chopper 2 gang phase and seeing the 1 spot split into 3 distinct spots. If you see 1 spot and proper dechopping is verified on ITV0I05, insert ITV0I06 and verify that there is 1 spot there as well and that it splits into 3 spots with the chopper2 gang phase. If you do not have proper dechopping in Chopper 2, continue this procedure.

5. If you see 3 distinct spots on ITV0I05 that are almost centered, insert ITV0I06. If the spots are coincident and centered on ITV0I06, chopping is set up pretty well and you probably don’t need to set up dechopping. If you don’t see nice spots on ITV0I06, continue on.

6. If you see only 1 spot on ITV0I05 that does not break into 3 spots by rolling gang phase:

1. Make sure that all 3 lasers are on and that all 3 slits are in proper position. If you are using a high polarization laser for one of the beam, you may need to retract that slit fully to see any beam on the viewer. Double check attenuator settings to ensure that an adequate amount of beam is striking upstream viewers.

2. If you still see only one spot on ITV0I05, try steering using MBH0I05 and see if you can find the other spots. It may be impossible to have all three on the screen at once - note the direction that beams disappeared so that they can be brought back. Bring the spots back onto the viewer by moving the chopper 2 gang phase (if they are all in different directions) or by adjusting the Chopper 2X and/or Chopper 2Y phases until you can see them all on the screen. The goal is to have all three near the center of the viewer.

3. Once you can see all three spots on ITV0I05, it is time to adjust both Chopper2X phase and gradient.

a. To setup, record starting values of Chopper 2X and 2Y GRADIENT, then reduce the gradients by ~30%. This will spread the spots out on the viewer.
Initial 2X gradient: ________________ Initial 2Y gradient: ________________________

b. Set the lens MFA0I05 to 1500 mA, insert viewer ITV0I05 and observer the three spots as pictured below (inverted triangle). If the pattern is a triangle, but is rotated, adjust the gang phase of Chopper 2 until the pattern is exactly as shown.

c. Adjust the Chopper 2X GRADIENT until the two upper spots (which are for the A and C slits) are aligned on top of one another. Record this good value of Chopper 2X GRADIENT here: _______________.

e. If the spots are not aligned directly over one another, adjust the Chopper 2X PHASE until the spots are in a vertical line. This will be the proper setting for the Chopper 2X PHASE. Record the value of chopper 2X phase here: ______________.

f. Reduce the chopper 2X Gradient by ~30% to obtain three beam spots (as in step 4b)

g. Adjust the Chopper 2Y Gradient to align all three spots into a line. Record the value of Chopper 2Y Gradient here: _______.

h. Adjust Chopper 2Y Phase to until the line is horizontal. Record the value of Chopper 2Y Phase here: _________.

i. Adjust chopper 2X gradient back to the value recorded in above.

j. Record Chopper 2 GANG PHASE here:________ All three spots should be coincident. Roll Chopper 2 gang phase to verify that the three beam spots open and collapse into a single spot. Set Chopper 2 gang phase to the recorded value when finished so that a single spot is produced.

k. Return lens MFA0I05 to previous value (most likely 982 mA) and put it back on loop.

l. Reduce MFA0I06 to 878 mA.

m. Insert viewer ITV0I06 and look for three beams coincident near the center of the viewer. Verify dechopping by rolling Chopper 2 gang phase and seeing the spots break into 3 and come back. If the dechopping does not look good on ITV0I06, the chopper 2X gradients are most likely to high. It is quite difficult to get good dechopping on both ITV0I05 and the rest of the viewers. Looking at ITV0I06, reduce the chopper 2X gradients slightly until the spots become coincident. Verify that the spots remain close to coincident on the downstream viewers. Offsets of 1 mm are common but undesirable.

n. Return MFA0I06 to the previously recorded value and put it back on loop.

. NOTE: If chopper phases have been changed, the phases of the capture, 1/4 cryo unit and the full cryo units must be optimized following procedures listed below before injector setup is complete.

Buncher centering

Prerequisites:
    a. Beam threaded to ITV0I06
    b. Choppers set up, Slit B to 32.5 mm
    c. Viewer limited mode beam (pulse width at default of 10 usec)
    d. Buncher RF on

Procedure:
1. Record buncher amplitude here: ________________ (should be 16.45 )

2. Set buncher amplitude to 18 on Gset (5.5 keV cavity voltage?)

3. Record current bunchlength modulator frequency here: ___________Hz (nominally 36.45 Hz)

4. Set bunchlength modulator frequency in the range 62-64 Hz

5. Record Bunchlength phase amplitude here: _____________ (nominally 25)

6. Set bunchlength phase amplitude to 45

7. View viewer limited beam on viewer ITV0I06

8. Turn ON bunchlength function generator

9. Steer with corrector magnet MBH0I05H/V until beam motion is not visible.

10. Restore buncher amplitude to value recorded in step 1.

11. Restore bunch length modulator frequency to value recorded in step 3.

12. Restore bunch length phase amplitude to value recorded in step 5.

13. Turn OFF Bunchlength modulator.

Look at position of spot on ITV0I06, and record X and Y positions of spot. (This needs to be somewhere for reference)

Buncher phase/amplitude setup

A buncher phase and amplitude setup procedure exists in the ops documentation. However, this procedure is rarely (never) needed and thus is omitted here.

Capture Phase/amplitude setup

Prerequisites:

a. viewer limited and tune mode beam will be used
b. Master slit and central plug should be in
c. Beam centered in buncher
d. Buncher off, but buncher phase and amplitude setup
e. Beam centered on 500 keV spectrometer viewer?????????????
f. Capture section on at GSET = 5800 (units)
g. Beam must be steered through center of capture section)

Procedure:

1. If buncher and capture need only to be verified, go to step 7.
2. Crest capture section for initial gradient value (Vary capture phase; beam should be at leftmost part of arc on the 500 keV spectrometer viewer ITV1D00 when capture is on crest)
3. Enter 663.25 mA into MBO0I06 and run hysteresis program.
4. If gradient needs to be set, adjust capture section gradient so that the high energy end (left end) of the beam smear is centered on the screen
5. Add 16.5 degrees to capture phase
6. Turn on buncher; beam should collapse to a spot centered on viewer ITV1D00. If so, buncher and capture are set up.
7. Verify buncher and capture phasing:

a. Turn off buncher and subtract 16.5 degrees from capture phase and verify that capture is on crest (Vary capture phase; beam should be at leftmost part of arc on the 500 keV spectrometer viewer ITV1D00 when capture is on crest)
b. Turn on buncher and subtract 19.5 degrees from buncher phase. Beam should be a centered spot on viewer ITV1D00. An increase or decrease in buncher phase should produce lower energy beam (higher energy beam moves to left on ITV1D00)
c. Add 16.5 degrees to capture phase and 19.5 degrees to buncher phase. Beam should again be a centered spot on ITV1D00.

8. Note: If buncher RF phase is changed, downstream RF elements (capture, 1/4 cryo, full cryo units) must be optimized to assure that the injector is properly set up.

Capture Centering

Prerequisites:

· Master Slit and Central Plug in

· Beam setup properly through chopper

· Viewer limited mode beam

· Buncher and Capture RF on

· Buncher gradient and phase set (not typically ever changed)

· Capture gradient and phase set as per Capture Phase/Amplitude Setup procedure

· Beam threaded through capture to viewer ITV0I06A

· Beam centered in Buncher as per Buncher Centering Procedure

Procedure
1. Record bunchlength modulator frequency here: ______________ then change it to 64 Hz.
2. Record bunchlength phase amplitude here: _______________ then turn it to 20.
3. Turn on bunchlength function generator
4. When correctly set up, the following conditions are satisfied:
a. The only motion that should be visible on ITV0I06A is a slight "breathing" of the beam and
b. The beam should be nearly centered on viewer ITV0I06A.
5. If horizontal or vertical beam motion is present and/or beam is not centered on ITV0I06A, first try adjusting correctors MBH0I06H/V so that the motion is minimized.
6. If motion is still present, first verify that the beam is centered in the buncher.
7. If the problem was not buncher centering, Adjust MBD0I06AH/V to center beam on viewer then use MBH0I06H/V to center the beam in the capture. Do this iteratively until beam motion is eliminated.
8. Restore Bunchlength modulator frequency and phase amplitude to values recorded in steps 1 and 2.
9. Turn off modulator.
10. If desired, capture beam position on the viewer using the DATACUBE software and analyze to determine position. Record appropriately.

A3/A4 centering

Prerequisites:
    a. Beam centered in choppers (see chopper centering procedure)
    b. Beam properly dechopped (see chopper1, chopper 2 phase setup)
    c. Buncher Properly setup (both buncher centering and buncher phase/amplitude)
    d. Capture properly setup (both capture centering and capture phase/amplitude)
    e. Both viewer limited and tune mode beam will be needed

General steering in this region:

Use 0I06 corrector to center on the capture

Use 0I06A to center on the A3 aperture

Use 0I07 to center on A4

Use 0I07A to center in the quarter as viewed by viewers and BLMs 0L01 and 0L02 (orbit MUST be flat on BLMs 0L01 and 0L02 to avoid trips)

1/4 cryo centering

Prerequisites:

Viewer limited and Tune mode beam will be needed
Buncher must be properly setup
Capture must be properly setup
Beam must be centered on apertures A3 and A4
Beam must be threaded through to viewer ITV0L01
Quarter Cryo gradients as follows: IN02-7 gradient = 4.840, IN02-8 = 4.829 (this gives 5 MeV at 0L01)

Procedure:

· If the 1/4 cryo unit is not roughly crested, turn the unit off and thread the beam through. Then turn on the RF in IN02-7 and adjust the phase until the best beam spot appears. Then turn on IN02-8 and again adjust the phase until the best beam spot appears.

· Pull up the bunchlength modulator frequency controls and record the modulator frequency and phase amp here: ____________

· Set the Bunchlength modulator frequency to 62 Hz and the phase amplitude to 20.

· Steer with MBD0I07AH/V until modulation is not visible on viewer ITV0L01. Finer adjustment of centering in the unit can be achieved by viewing the beam at ITV0L02 or ITV0L03.

· If motion can not be eliminated by using MBD0I07AH/V, the beam is probably not centered in the buncher or the capture. Begin by trying to resteer through the buncher, then try the capture.

· Repeat steering with MBD0I07AH/V until satisfactory.

· Restore the Bunchlength modulator frequency and phase amplitude

· Turn off the modulator

· Use the DATACUBE data acquisition and record the position of the beam at viewers ITV0L01-ITV0L03.

Cresting 1/4 cryo unit

Procedure:
The procedure for cresting the 1/4 cryo cavity has been automated. Typically, a measurement of bunchlength in the yao cavity is first made, then the 1/4 cryo unit is crested. The bunchlength script can be accessed through the injector startup procedure, or by pulling up a program called bunchlength alone. Cresting the quarter cryo unit is accessed through the injector startup procedure

Cresting 0L03 and 0L04 RF

In order to crest the 0L03 and 0L04 regions, two different methods can be used. The first involves cresting while looking at the viewer ITV0R04 while the other sends beam into the 45 MeV spectrometer dump and crests it there. Cresting on the viewer involves less time and setup, as it uses the bend that is already present in the chicane, while cresting in the 45 MeV spectrometer can be more accurate since it can be done in CW mode and uses a dedicated bend dipole for the cresting. Both methods will be explained here.

Cresting using viewer ITV0R04:

Prerequisites:

a. Beam through the injector Chicane to the 45 MeV dump

b. Viewer limited mode beam

Procedure:

1. Turn on viewer limited mode beam and look for a spot on viewer ITV0R04

2. Adjust intensity of spot until it is bright enough to see but persistence is not to large

3. Adjust the phase of the RF in the 0L03 cavity, starting with the gang phase. Since the dipole before the viewer is bending the beam to the right, the highest energy is when the spot has moved to the leftmost position on the viewer.

NOTE: If you need to move the beam spot over on the viewer, use corrector magnets 0R02H or 0R03 H to get the beam back onto the viewer. Make sure to back this step out before trying to send beam to the dump after cresting.

4. After working through each of the phases of the individual cavities in the 0L03 region, go back and readjust the gang phase. Readjust each cavity phase again as well, iterating until no changes are necessary.

5. Start adjusting the gang phase of the 0L04. This is where the 10 degrees of compression are added, so the gang phase is quite likely at least 10 degrees off crest. Use the corrector magnets noted above if you need to move the spot to keep it on the viewer.

6. Once the 0L04 gang phase is crested, crest each cavity individually. Repeat cresting gang phase and individual cavities until optimized.

7. If major adjustments were needed, you may want to re-crest the 0L03 region then the 0L04 region. This is not necessary for small adjustments.

8. To set up for running, once the cryo RF is optimized, add +10 degrees to the gang phase for 0L04. This will introduce the proper compression for beam delivery to the machine.

0L07 Spectrometer Measurement

Current procedures for an injector energy measurement and adjustment exist. Please see document NCC-PR-02-006 under the Injector Procedures.

Injector Chicane setup procedure

QE scan (wafer scan) procedure

An up-to-date procedure for QE scanning exists