From: boettcher@physik.uni-kiel.de (Stephan Böttcher)
To: solo_kiel@physik.uni-kiel.de, change4@physik.uni-kiel.de
Subject: flyrena L2 trigger
Date: Sat, 27 May 2017 20:43:24 +0200
Message-ID: <s6ninkmp2cz.fsf@blaulicht.brux>
Moin,
I found a deficiency in the flyrena L2 trigger, that may affect HET/EPT
and/or LND.
If multiple L2 trigger are satisfied by a particle hit, the L2 trigger
bits are set as soon as one of those L2 trigger conditions is satisfied
and the event record is generated according to that triggers readout
mask. A more elaborate trigger may come active one or more ADC clocks
later, but that will not be reflected in the L2 trigger bits, nor the
selected readout mask, nor the L3 trigger being activated.
HET/EPT is probably not affected. But that needs to be verified.
The current LND configuration is affected.
Assume a charged particle hit. Detector B triggers an ADC clock earlier
than A and/or I, so that the total-dose-in-B trigger fires with a narrow
readout mask, calling for dosimetry L3. One ADC clock later, the
condition for the charged particle trigger is fullfilled, but the event
readout is too narrow, and the wrong L3 trigger is called.
A workaround is to never do sparse readout, i.e., always read all
channels, and add code to L3 to refine the triggers.
Gruß,
Stephan
PS: I found this problem in the data of the RpiRENA mADAM detector for
the weather ballon flight this summer. That is a direna filter
with 3MSPS and 12-bit coefficients, so the probablility for triggers to
come out of time is higher.
git-svn-id: svn+ssh://asterix.ieap.uni-kiel.de/home/subversion/stephan/solo/eda@6069 bc5caf13-1734-44f8-af43-603852e9ee25
