Installation notes for active collimator beam test 2007

Preparation notes for active collimator beam tests to take place in Spring 2007. The online accelerator schedule shows that there will be significant photon running in Hall B in 2007.

• 2-20-2007 [R. Jones] I made an initial contact with Pawel Nadel-Turonski, spokesman of g13. G13 is scheduled for running in Hall B 3/8 - 5/29. Pawel welcomes us to conduct active collimator tests in parasitic mode during this period. The beam endpoint energy will gradually increase throughout this period, starting at 3.30 GeV and ending at the top accelerator energy of 5.16 GeV.

• 3-12-2007 [F. Klein] We have a stage+motor available (horizontal motion up to 1.5m). I checked the VME motor drivers in the Hall-B forward carriage but strangely all channels are connected (although I cannot recall more than 2 motors used in the alcove). I'll find out where the cables go next weekend. For sure, I'll have epics controls running for the stage!. I was looking for a table but haven't found Tom Carstens who keeps the stuff somewhere (that's easy to solve!). I connected some cables running from the forward carriage to the Hall-B counting house (in case that we want to look at discriminator signals).

• 3-19-2007 [F. Klein] There is a EPICS stepping motor controller located on the CLAS forward carriage that supports 4 motors. Right now two of them are connected on both ends, and the other two are connected only on the controller end, and are available for the translation stage motor. A motor requires two cables for the stepping motor control and also the limit switches. Franz has these cables and will provide them. We need to move a table into the alcove (Franz thinks one is available that is about the right height). Things we still need are:
  • support wedge for active collimator
  • ethernet and power for the PC
  • schedule time to install the table and collimator
  • schedule survey crew to align the collimator

• 3-19-2007 [R. Jones] If possible, I would like to install the detector during the week of March 26. The collaboration meeting is Thursday-Saturday.

• 3-26-2007 [V. Burkert] Thanks for the detailed description of the proposed test setup in Hall B. In general, I have no objection to doing this if it doesn't interfere with the running experiment. I do see a potential that there might be something like a "red flag" in that you want to continuously run this test. Hall B has currently quick access to the Hall without having to survey the Hall for radiation due to the generally very low level of activation in the Hall and in the beamline area. If your active collimator is continously exposed to the photon beam it may develop a high enough activation that Radcon may not allow the same procedure to continue. Therefore, I suggest that you work with Radcon to make sure that we will avoid such a situation. Additional shielding of the collimator area maybe sufficient, but Radcon clearly needs to be involved in setting this up.

• 3-26-2007 [V. Burkert] By the way, today I was made aware that the machine maybe running through Tuesday. If that is the case then Hall B will remain closed. So, you may want to check with the counting house (x5244) what the situation is.

• 3-26-2007 [E. Smith]
  • First, the entire activity must have not impact on the running experiment g13. For example, the location of the collimator was going to be placed upstream of the photon profiler and the total absorption counter (TAC). The profiler is currently of limited use to g13 according to Pawel, but for normalization runs, the collimator cannot be in front of the TAC. Berhard proposed using the same table as the TAC which would automatically have only one device in at a time. However, this would need to be checked very carefully so that normalization runs proceed normally. Alternatively, if the collimator can be placed downstream of the TAC, this might solve all monitoring issues related to g13. I am not sure how much room there is. Please check with Stepan and Dave Kashy on options related to the position of the collimator along the beamline.
  • Second, we need to review any radiation conditions as Volker has already stipulated.
  • Third: alignment. The note by Richard requests alignment of the collimator to within ± 1 mm. This will not be trivial to achieve since the collimator is back in the alcove where alignment marks may be a challenge. I suggest Richard review this requirement. Why is 3-4 mm alignment not sufficient? (If the survey crew is required this also needs to the scheduled). This could be achieved with a ruler if the height of the floor is known. Do we need any adjustment left-right to check sensitivity to beam position?
  • At the moment the schedule calls for the hall to be open Wed-Sun, but is not firm. The accelerator will likely need time for changing the energy of the machine and might need to lock up Hall B.

• 3-26-2007 [F. Klein]
  • We want to set up the collimator in the front part of the alcove. The lateral motion of the motor stage that Stepan has available is 1.5m, which is more than enough to move the collimator out of the beam. I think we cannot position the setup behind the TAC (and gamma profiler) since there is hardly any space. Bernhard's idea to attach it to the TAC motor stage won't work either because it requires to attach the motor stage to the existing TAC (looks like complicated mounting) and I don't think there is any space for the setup on the right side when the TAC is in the beam.
  • Richard agrees that the survey group doesn't have to be involved. It's sufficient to use a ruler and laser pointer with level!
  • Volker's concern about increased radiation has to be addressed: we'll contact Radcon on Wednesday concerning the issue.

• 3-29-2007 [F. Klein]
  • We presented the project to RadCon shortly after lunch. Erik Abkemeier advised us to position the collimator in the cave where gamma profiler and TAC are located. This way they can insure that the rapid access mode is still available even in the unlikely case that the collimator gets activated. They want to survey the setup after a day of beam (during next accelerator beam studies) in order to ensure proper radiation control. If any activiation is found, the 'TAC' cave will be separated via a rope and any work there would require a sweep.
  • With Krister's help we mounted the setup onto the TAC - thus behind any equipment used for beam monitoring, and in case of normalization runs the collimator will be out of the beam. In order to use the collimator in beam position, the horizontal TAC motor has to be moved - but not the vertical(!), i.e. the TAC will be still out of the beam.

• 3-29-2007 [S. Stepanyan]

In all this you missed one important detail: the run plan - how often you are going to move the collimator into the beam and how often beam line pager will be ringing because TAC will not move due to security we have in place to prevent "frying" it. Since I am caring the pager I want to know the plan and want to be notified in advance before TAC or any thing will move in and out of beam.

• 3-30-2007 [D. Tilles]

Once there has been beam in the hall, you will need to have it checked by rad con before you go in [the forward alcove area where the TAC is located], unless you just plan to look at it. The RWP says "no hands on work" with out the survey. Volker has said that is the way it is.