E99007 , GEp(II)
Here is a list of things that have to be done in the summer,
while the Hall is open (August-September). This page is updated as work
goes on.
-
Calorimeter -
The calorimeter is an array of 147 15*15 cm2 blocks of Lead Glass. 45 of them come from the pion rejector (the same we have used for previous tests, and 96 are taken from the shower detector in electron arm. The bad news is that those 96 blocks will have to be wrapped, since they are not properly wrapped in the electron hut, as they are in an opaque box. It can take up to one hour for a single block, light leak test included, so it is a considerable amount of time. We will have to make up a schedule for this tasks, with as many volunteers we can find. Information will come soon.
The platform the calorimeter will rest on will be ready beginning of September. At that time, we will have to mount the calorimeter on it, block by block (those who don't know will discover how heavy these babies are...), and then to test them again for light leaks, to make sure no damage has been done during transportation.
It would be nice if sometime before the experiment (during some maintenance period in e97111?) we could do a test of the calorimeter with beam on it, and adjust high voltages. 2 shifts would be enough, maybe even just one, with our experience.
There will also be some tests to do in September, when the calorimeter is assembled:
- Install (with
technicians help) 300 signal cables.
- Connect
the HV cables and test them.
- Test ADC
and TDC patch panels.
- Test CAMAC
crate, each of 10 discriminators.
- Check on
every TDC output signal.
- CH2 analyzer -
For this experiment, protons up to 3.8 GeV/c will be detected, so that the graphite analyzer of the FPP has to be replaced by polyethylene CH2, with higher analyzing power. This will come in two sets of plates to stack. The upstream set is 40 cm thick, and the downstream set is 60 cm thick. A frame has been built to support these plates between the open carbon doors of the FPP. During the experiment, we will (very probably) use both sets, so a total of 100 cm.
As of 8-1-2000, the plan is to fix the frame on the FPP
when it is on the floor in August or September. Then after e97111, take
straight through data to check alignment, and after that, stack up the
plates on the frame. To be as efficient as possible on this last part,
it might be good to do some kind of rehearsal when it's on the floor.
HV cables are connected to the blocks and to the HV supply. Cables are running along the Right spectrometer, and will be connected to the patch pannel as soon as the detector stack is back in (probably Friday).
The plan is to make a cosmic ray test by triggering with 4 big scintillator pannels, and then check signal in each block. That would allow to check the connections, the detector map, and the software. This test is expected to occur during the maintenance period mid -October.
We also ask for 2 shifts of beam time during 26-29 October
facility period, to allow for calibration.
The calorimeter is now stacked, it is on its platform, lifting the ensemble has been tested, and is possible, and everything is well. I will soon put some nice pictures of it. The flat cables that connect the TDCs to the discriminators are installed on the detector stack. The 50 remaining TDC cables are ready, and will be brought to the hall this afternoon. Wednesday will probably be the day we run all 300 signal cables in the right detector hut. I guess after that, we will be close to ready (or at least for the moment).
The FPP is in the configuration it will have in the October run (C1, C3 and C4 installed, C2 out). All major leaks have hopefully been fixed in every chamber.
The main remaining job to do is to modify the software
(ESPACE) to adapt it to the particular configuration we will run.
The platform is in the Hall. Right now, there are 3 separate parts (that will be hopefully eventually assembled). The platform itself (the white piece, if you are curious enough to have a look in the Hall), the upper frame in which the blocks will be stacked, and which will rest on the platform, and a lifting frame. This last is a 4-legs frame that will be mounted on the platform, and which will be the actual part attached to the crane when moving the calorimeter.
The blocks will be stacked in their frame on the floor, and the ensemble will then be mounted on the platform. Right now, and until late next week probably, technicians are designing and building a device to lift this 5 tons piece on the platform, without breaking anything (how nice from them !) As soon as this is done, we will start stacking the blocks.
A number of transverse bars (probably 8 or 9) will be mounted on the lifting frame, in front of the phototubes. HV and signal cables will rest on these bars, to decrease their weight on the tubes and bases.
On the FPP side, C1 is back in the stack, and reconnected.
C3 and C4 are being gas-leaks freed. This work will take until the end
of next week.
All 96 blocks from shower counter are now rewrapped. All blocks and bases have been tested, and a total of 3 PMTs and 2 bases don't work and need to be replaced (for the PMTs) or fixed (for the bases).
The 50 signal cables we used in the Spring test and that were hanging from the Left arm are now on the floor. We also received this morning the 30 remaining ADC signal cables. These cables are now being grouped by 9. We expect the 150 TDC cables any time now (probably the end of the week).
Gerfried, Ron and Sirish keep working on the leaks in Chamber 4. They should be done by the end of the week.
86 blocks are now ready. 80 of them have been tested, and we found 3 bad phototubes and 2 bad bases. The bases will be repaired by electronics lab, and we have up to 4 spare phototubes. The typical cosmic signal from a shower counter tube is between 5 and 10 mV at 1800 V. That corresponds to about 60 MeV cosmic rays. So for a minimum energy of 1200 MeV for the electron during the experiment, the signal should be about 20 times bigger (100-200 mV).
It has been decided at yesterday's meeting that it was not really necessary to rewrap the 47 blocks we used in May. Those are light-tight, and even though they have some significant amount of dead space due to thicker wrapping material, it shouldn't be critical, specially if we place them on the periphery of the calorimeter. That means that we only have 10 to go, which should be done by Monday. HV cables are now in the Hall, along with HV supplies.
On the FPP side, CH2 has
been installed, it takes about 1 hour for the procedure itself (add some
more time to install ladders ...). It will be removed on Monday, to allow
the October experiment to run. Gas leaks in chamber 4 are being worked
on.
58 blocks are now wrapped (and we are getting kind of
tired of the exercise). 10 of them have been tested on cosmic rays, and
all of them work fine, but one.
HV cables for the calo are ready, and 70 signal cables
are ready too. We are waiting for the delivery of 180 more signal cables
(ADC + TDC). So far, everything is on schedule.
The backframe for CH2 has been installed, and it just
awaits for us to stack it with polyethylene (probably thursday or monday).
41 blocks, out of the 96 from the shower, have been wrapped. The work goes well, we should be done by the end of next week. The 47 blocks from the pion rejector (the ones we used for the test in May, and which we need to rewrap tighter) should be finished within one more week.
Work on the FPP is also underway. Chamber 1, 2 and 4 are
currently on the floor. This will enable us to work on the gas leaks, and
drill some holes to place the CH2 frame.
We will then rehearse for the installation of the frame in the stack, and
of the analyzer in the frame. This rehearsal will also help us take a decision
on the chronology of events just before the experiment (removal of unused
Cerenkov, installation of analyzer, ...)
Sasha and Olivier started developing the technique for wrapping the blocks. One block is done, and has about 40 nA of light leaks (we accept up to 100 nA). The cosmic signal is very nice (~120 ns wide, ~40 mV amplitude). Tomorrow, the technique will be completed, and hopefully, most of the material will be brought down in the Hall, so that "production wrapping" can be started as early as Wednesday.
They also started testing discriminators (10*16 channels)
for timing. Just one has a bad connection that needs to be fixed (electronics
lab).
Today starts the 2 months down period of the Hall A to
allow the swap of the two spectrometers. This job will mainly be done by
the technical staff (see Jack
Segal's
homage)
During this period we will have to prepare the calorimeter,
and rehearse for installation of CH2
analyzer.