[Halld-tagger] photon beam wg meeting this morning

[Richard Jones]

Hello,

It seems that nobody at Jlab is going to be around for our meeting this morning.  I propose that we cancel and instead exchange whatever information we need to through email this time around. Here is a summary of what is going on with us here at UConn.

 1. Yang got back to me with the results of his new field map calculation with TOSCA.  He has made separate maps for the quadrupole and the dipole.  Here are the geometry specs he used.
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           For the quadrupole magnet, the step sizes are 0.1 cm in x y directions, 1 cm in z direction. The number of points are 41 in x and y directions and 101 in z direction (From -2cm to 2cm in x and y direction, and from -50 to 50 in z direction).  Left handed coordinate system, the origin is at the centre of the quadrupole magnet.

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          For the dipole magnet, the step sizes are 0.3 cm in  y direction, 1 cm in x and z direction. The number of points are 101 in x directions and 6 in y direction and 401 in z direction(From 0cm to 100cm in x  direction, and from 0 to 1.5 in y direction, from 0 to 400cm in z direction) .  Left handed coordinate system, the x origin is at the centre of the inner edge of the dipole magnet pole, and the y and z origin are at the centre of the dipole. For the dipole magnet, you have to use the symmetry to get map for the whole magnet.

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          The default steel BH curve in TOSCA has been used. All the dimensions are from the drawings.

 2. I will post these new files in a public place, and create a modified version of the gxtwist geometry to incorporate them.
 3. I asked Yang for copies of the geometry files that he used for TOSCA.  Either he overlooked the request or he would prefer to collaborate with us rather than share the files.  That is fine with me.
 4. We are planning on a site visit from the Jlab Readiness Review team on Feb. 7.  We are working on a construction schedule for the contract.
 5. Hovanes has been working with us to develop a spec for the bias supply controls for the microscope readout.  These discussions have hit on an issue of capability: whether we need to be able to read back the currents on each of the individual SiPM's in the system.  Currently we can read back all of the individual set voltages, but sense voltages on only 17 out the 510 channels.  Adding the additional current and sense voltage readback would entail some additional hardware on the control board and additional code in the FPGA.  We are at the point now where a decision on this should be made.  Perhaps a dedicated meeting over the next week should be arranged with Fernando, Sascha, and others.
 6. We had a meeting last week with members of the accelerator group to hash out specifics of the interface between the active collimator and the electron beam controls.  A draft spec for this interface is being developed at Jlab, and will be shared with us for feedback before it is finalized.

-Richard Jones

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