[Halld-tracking-hw] New preamp - resending table
Yves Van Haarlem
yvhaarle at ernest.phys.cmu.edu
Fri Apr 9 10:19:12 EDT 2010
I think the formatting got weird up in previous mail:
HV-board-ch || old-cable ch# || new cable ch# || fADC ch#
24 || 1 || 1 || 1
23 2 2 2
22 3 3 3
21 4 4 4
20 5 5 5
19 6 6 6
18 7 7 7
17 8 8 8
16 9 17 !
15 10 18
14 11 19
13 12 20
12 13 21
11 14 22
10 15 23
9 16 24
8 17 9 ! 9
7 18 10 10
6 19 11 11
5 20 12 12
4 21 13 13
3 22 14 14
2 23 15 15
1 24 16 16
/--------------------------------
/ Yves Van Haarlem
_--~~--_ /
/~/_| |_\~\ / Carnegie Mellon University
|____________| / Department of Physics
|[][][][][][]|:= / Wean Hall room 8404
__| __ |__ \ Pittsburgh, PA 15213
| ||. | == | | \ USA
(| ||__| == | |) \
| |[] [] == | | \ Tel.: +1 412 268-6949
| |____________| | \ +1 412 641-9252
/__\ /__\ \ Fax.: +1 412 681-0648
~~ ~~ \-----------------------------------
On Fri, 9 Apr 2010, Yves Van Haarlem wrote:
> Hi Fernando,
>
> I have a suggestion below,
>
>>> My other concern is over the mapping of the preamp channels through the
>>> cable. We are now using the new preamp and new cable with the old HV
>>> board. The correspondence between the numbering on the HV board and the
>>> preamp channels has changed. Is this now the final mapping?
>>>
>>> Previously we were using the cable with channels 1-8 and 17-24 feeding into
>>> the shaper unit, which has 16 channels total, and then into two 8-channel
>>> fADCs. The chamber prototype is configured so that the missing 8 channels
>>> correspond to the straws along 2 sides of the chamber; the two groups of 8
>>> channels in use correspond to two blocks of 8 straws, one above the other.
>>> With the new cable it seems that we now have access to the 8 channels which
>>> were missing before (along the edge), but since we only have 16 channels
>>> from the shaper, we have lost access to one block of 8 straws. This makes
>>> cosmic ray tracking much slower, since we are looking for tracks passing
>>> through at least 4 straws. This is hard to explain without a diagram but
>>> the effect is that the configuration of our available channels is much less
>>> as efficient than before. This will be solved when we have a 72-channel
>>> fADC; alternatively we could just use the old cable until the new fADC is
>>> available.
>>
>> The old preamps (also designed for 24-channels) had only two chips installed
>> (on top) because the ASIC package was not reliable for assembly on the bottom
>> (it had a removable lid in case we needed to probe the die). The preamp card
>> has channels 1-8 from one chip on top, 9-16 from bottom chip and 17-24 from
>> the second chip on top. Because of the 16-channel readout on the shaper, the
>> cable (old cable) was modified at the ERNI connector (connects to preamp) to
>> read channels 1-8 and 17-24. This is the reason for what you observe with the
>> new cable. This won't be the case with the 72-ch fADC125 because it reads
>> from all 24 channels on a preamp card. Yes, please you use the old cable with
>> the new preamp and shaper for your immediate tests and then use the new cable
>> when the 72-ch fADC125 becomes available (late April).
>
> Once it is decided which group of 8 channels goes where on the cable
> (between HV-board and fADC), could you modify the labeling of the channels
> on the HV board so that channel 1 -> 24 on the HV-board corresponds to
> channel 1 -> 24 on the fADC (or 25 -> 48; or 49 -> 72). We might avoid a
> lot of confusion in the future.
>
> The difference in mapping between old and new cable in a table:
>
>
> Ch# on HV board || ch# on old cable || new cable || fadc#
> 24 || 1 || 1 || 1
> 23 2 2 2
> 22 3 3 3
> 21 4 4 4
> 20 5 5 5
> 19 6 6 6
> 18 7 7 7
> 17 8 8 8
> 16 9 17 !
> 15 10 18
> 14 11 19
> 13 12 20
> 12 13 21
> 11 14 22
> 10 15 23
> 9 16 24
> 8 17 9 ! 9
> 7 18 10 10
> 6 19 11 11
> 5 20 12 12
> 4 21 13 13
> 3 22 14 14
> 2 23 15 15
> 1 24 16 16
>
>
> So the possition of two chips have been swapped on the cable, was this
> deliberate?
>
>
> Best regards,
> Yves
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