December 13, 2006 online meeting minutes

presented: Sergey Boyarinov, David Doughty, Mark Ito, Elliott Wolin, Vardan Gyurjyan, Sergey Pozdnyakov, Nerses Gevorgyan, Ed Jastrzembski

We had very useful discussion on CLAS12 trigger design. The project was discussed already on a meeting few days before involving Volker and Latifa so we had already general directions and Sergey prepared preliminary document (see attachment). Today we are concentrated on several issues which were not completely understood. One of them was how we can search for clusters in calorimeter(s) using JLAB Flash ADC SUMs as trigger system inputs. It seems possible to identify cluster position but unclear how to obtain cluster energy. We decided to put coordinate-based cluster finding into design along with energy sum for predefined parts of calorimeter(s), and keep cluster energy finding as an option. Several other aspects were discussed, such as the possibility to use coincidence-based logic instead of latching-based, usage of SYNC and ASYNC inputs as it is done in current trigger system, missing trigger bits in TS latch register for multilevel triggers etc. More meetings will be held to clarify remaining details.

G13 run was shortly discussed. Our time profiling system identified TAGE2 ROC as the current bottleneck. New v1190/v1290 CAEN TDC firmware conveniently arrived and was loaded into TAGE2 ROC TDCs, and readout library was optimized as well. As result we were able to increase event rate from 8kHz to more then 9kHz at dead time around 15% (can be viewed using online timeline plots). Elliott fixed logbook acknowledgments and run_summary script.

We also talked about SY1527 incorporation into EPICS and about counting room test setup for old Lecroy HV mainframes. Both projects goes well: we have medm GUIs working, new classc0 IOC was installed in counting house along with one Lecroy mainframe, and Delisa is working to fix 4 more LECROY mainframes. classc0 will be used to test Lecroy mainframes and HV boards before installing them to the Hall. Nerses is working to produce documentation for SY1527 incorporation into new EPICS and on Linux IOC in general. Classc0 is running old EPICS. It maybe useful to try to convert classc0 to new EPICS to identify corresponding problems.

Attachment: CLAS12 trigger project: short-term plan (Dec 2006-May 2007)

Overview

The goal for 6 following month is to develop principal scheme of
trigger system for June 2007 CD2 review. Plan includes 3 steps:
preliminary design (Dec 2006), CLAS data- and simulation-based
efficiency studies (Mar 2007), electronics design (May 2007).

Preliminary design

CLAS12 trigger system consists 3 levels discussed below:
Level 1 is based on information from 6 detectors: forward and
preshower calorimeters, forward and central time-of-flight counters,
high- and low-threshold cherenkov counters. Level 1 must have
a possibility to include additional detectors during CLAS12
operation if needed.
Three kind of information will be used in Level 1 trigger: time,
position and energy. Time information will be enforced by the
nature of trigger logic which is based on coincidence strobe with
100+ MHz frequency. Position and energy can be obtained from
pretrigger discriminators as it was done in CLAS, or/and from Flash
ADC boards.

Level 1 decision is based on energy cuts for pre-defined objects,
geometry cuts for position-based reconstructed clusters and
(optionally) energy cuts for reconstructed clusters. Matching of
different components will be used as well to set additional cuts and
provide extra information for matching with Level 2 trigger.
Decision time - tens of nanoseconds.

Level 2 is based on drift chamber hit information. It will perform
superlayer- or region-based segment finding and sector-based road
finding. Since existing ADB crates will be reused they will provide
an information for the replacement of old segment collectors and
following logic. Level 2 decision is based on road multiplicity cuts
and matching with Level 1. Decision time - few microseconds.

Level 3 is based on information from all CLAS12 components obtained
from DAQ and slow control systems. It will perform event rate and
event size reduction. We assume that full event reconstruction using
default geometry and calibration will be incorporated.
Preliminary design must be ready by the end of 2006. All three
level details will be finalized as result of CLAS data analysis to
be performed in three following month.

CLAS data- and simulation-based efficiency studies

It is very important to estimate an efficiency of every proposed 
trigger component. Following components must be studied:
- electron identification efficiency using cluster finding in both
calorimeters (coordinate-  and energy-based) in conjunction with
hits in time-of-flight and cherenkov counters;
- electron identification with and without proposed Level 2
information;
- possible trigger efficiency improvement for experiments without
electron identification and for experiments with multi-particle
requirements.
All efficiency studies must be completed by the end of March 2007.

Electronics design

Electronics design discussion was started and will continue until
March 2007, then actual principal scheme development will start.
It must be ready by the end of May 2007.