• RTV cookie/mold: The 25-cookie mold has been ordered. We will receive it early next week. We need to design some kind of table to hold the mold (so we can check air bubbles from below). For the 9/25-block prototype, we won't have time to make the cookies that way, we will use optical grease instead.

 
• Pb-glass radiation damage: David has brought the 30 deg block we've put in the hall 2 weeks ago. The side that faces the target is definitely darkened over a ~5 mm range. David will calculate the associated dose received during those HAPPEX runs. The short range of radiation damage indicates it's a very low energy background. One good thing about it is that it probably doesn't affect much the showers created by higher energy particles (the shower starts after the darkened area). in any case, we have to investigate a way to cure the damaged blocks, by a high power UV lamp for instance.

 
• Cooling system: Bogdan has ordered two 6" fans. Tom and Jeffrey have the responsability to build the box and manifold for the 25-block prototype. Tom brought a hose we can possibly use. Bogdan argued it seemed not flexible enough, and that we should look at latex hoses. Tom and Jeffrey will work on that too.

 
• Gain monitoring system : Once again we've discussed what we would use to monitor the gain. Specifically, do we want to attache the optical fibers to the back or the front. An additional issue here is that since the front will darken due to radiation damage, we may not even be able to get enough photons back on the phototube. Eugene suggests we only monitor the PMT, somehow directing the light from the optical fiber on the cookie. That way we are not affected by the radiation damage darkening (which once again may not affect the showers at high energy). This way to monitor the PMT gain requires to change the design of the Ti flange. Charles suggested we should think about it one more week before we settle on a design and order 750 pieces at once. Check out the discussion by Charles Hyde-Wright for more about the gain monitor system.

 
• Grounding issue: The housing grounding has been discussed. We should connect the base housing to the HV ground. After some discussion, we came to the conclusion we should get a wire out of each base and connect it to the housing on the outside with a crocodile plier (we may need to use copper tape to ensure a good conduction).

 
• Parts ordering: The JLab account is not setup yet. The first things we should order are the circuit boards and the sockets since they need a LOT of soldering. If we have those parts early enough, we can hire summer students to solder the components and wires to the circuit boards. We should keep in mind 1 person can make 5 complete circuit boards (with the socket glued to it and all the wires/components soldered) in 1 day. We need to make 750 bases...

 
• Circuit board: We have given-up the tongue idea (long circuit board with connectors). We now want cables going out of the base with cheap connectors. Also hakob has made some changes on the circuit board I will had, so we can order them pretty fast. 

 
 
Franck Sabatie - 04/28/1999


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