CALICE MAPS Meeting, RAL, 31/03/09
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Present: Jamie Crooks, Paul Dauncey, Marcel Stanitzki
Phone: Owen Miller

Minutes: Paul


Minutes of previous meeting: No comments or corrections.


Organisation: Paul asked about the future of these meetings relative to
 SPIDER. It was thought that meetings in this format should continue and
 would cover the TPAC1.2 testing. However, work for the DECAL stack,
 e.g. TPAC2 studies, should be reported in the SPIDER meetings.


Sensor fabrication: Jamie showed some slides (see usual web page), of
 which the first gives the TPAC1.2 submission status. The sensors should
 be sent back from the foundry on May 7, which means they will arrive at
 RAL a few days later.

 Paul reported that 20 USB_DAQ PCBs had been delivered to Imperial and
 Marcel says they have been paid for in this FY. Marcel reported that
 the components for the PCBs had been delivered to RAL and Paul will
 transport these back to Imperial. Marcel has also received the CAEN
 crate and two LV power supplies. These could be used for the TPAC1.2
 beam test this summer as a test of the system, but the crate is bulky
 so this depends on what transport is available.

 Marcel also has received a 20TByte RAID disk array and a server which
 will be used to store SPIDER data, including the beam test data.


Sensor testing: Jamie's other slides showed his work on aligning the
 laser optics. He had to build spacers to raise the microscope in order
 to accomodate the FORTIS PCB stucture. The laser has many alignment
 controls but it is not clear what they do. Changing the most obvious
 ones does not make an obvious difference to the effects shown on his
 slide 7. Jamie will contact the microscope manufacturers, either to get
 enough information on how to align the system, or to get them to come
 and do it themselves.

 Jamie had no new information on the possibility of halving the gain for
 the bulk pixels and has not yet checked the comparator on the TPAC1.0
 test pixels.

 Marcel showed some slides on Fe55 results; see usual web page. The
 scope is AC-coupled to the test pixels so the pedestal-equivalent
 should be zero. Note, the peak ratio quoted is just the ratio of the
 peak heights, not of the Gaussian integrals (which depend on the widths
 also). There has been no change to the system since the previous plots
 were made, so the relative positions of the high and low (i.e. the peak
 at ~1/3 of the Fe55 main peak) energy peaks should be directly
 comparable. To calibrate the bulk pixels, we need to know these peak
 positions ratio accurately. From Marcel's previous talk slide 6, these
 appear to be in the ratio 55.9/205.2 ~ 0.27. Also, to confirm the low
 energy peak is what we think it is, then the integrated Gaussian ratio
 of the two peaks is also needed.

 Both Mike and Renato were absent, so there was no news on using Diamond
 for testing sensors.

 Owen showed two sets of slides; see usual web page. The first shows the
 effect of a hit clustering algorithm, which delivers a list of clusters
 containing more than one hit, formed by combining nearest neighbours,
 including corner-to-corner. The clustering does not use the timestamp
 and so can potentially combine hits widely separated in time. Owen will
 send the code (implemented as a function) to Paul for inclusion in the
 code repository.

 Owen's second set of slides showed temperature measurements from a
 TPAC1.0 sensor. The "non-substrate" side is the top, i.e. the side with
 the wirebonds. The y axis scale on slide 3 is 2C/division for the red
 and grey lines and 0.2C/division for the green line.

 Paul showed some more results from the simple charge diffusion model,
 see slides on usual web page. These do not include noise and give only
 qualitative, not good quantitative, agreement with Marcel's Fe55
 measurements, e.g. the peak is at ~0.31 rather than the ~0.27 observed.


Next meeting: Due to the limited number of people attending, the next
 meeting will be arranged by email.