Time-of-Flight System Shift

Detector Description

The Time-of-Flight (TOF) consists of 92 scintillator counters arranged in two planes. The upstream plane has counters running horizontally and the downstream plane has them running vertically. Most have dimensions of 2.54x6.00x252 cm with exceptions noted below. The 46 counters in each plane consist of 42 counters with a PMT on each end, with 4 counters only read-out from one end (due to the beam hole in the center of the plane). Single-ended counters are of roughly half the length of the standard counters. In addition, the four double-ended counters nearest the beamline (two on each side) are of half-width (3 cm rather than 6 cm), to reduce counting rate.

The downstream counters have ends labeled "top" and "bottom" while the upstream counters have ends labeled "north" and "south". The PMTs themselves are numbered from 1 to 44 going from top to bottom or north to south.

The Time-of-Flight is located just upstream of the FCAL and downstream of the FDC. It is mounted on the forward carriage.

All PMTs in the system are the same: Hamamatsu H10534MOD. There are 176 PMTs altogether.

There are no devices providing environmental information (such as temperature) associated specifically with the TOF.

Shift Duties

Shift crews should be monitoring the following:

1. high-voltage status
2. statistical information from raw data ("monitoring histograms")

High-Voltage Status

In general, most important properties of individual HV channels will be monitored automatically by the EPICS alarm system and shift crews need to respond to alarms as they arise. To facilitate this, each shift should check that the TOF HV is up and running.

The conditions that may cause EPICS alarms are:

• tripped voltage
• read-back voltage out-of-range
• supply current out-of-range
• EPICS communication lost

In responding to alarms shift crews should check the guidance for the alarms as provided by the alarm handler.

Statistial Information

Each run produces a set of monitoring histograms that should be compared to nominal histograms and scanned for anomalies. The histograms include:

• occupancy, channel-by-channel
• end-to-end coincidence rates (where appropriate)
• geometrical distribution of plane-to-plane matches
• timing distributions

Trigger Monitoring

The TOF calibration trigger should be running at about 0.1 percent of the total triggers during normal running. If this is not the case contact the trigger or TOF expert.

Expert personnel

The individuals responsible for checking that the TOF is ready to take data and setting its operating parameters are shown in following table. Problems with normal operation of the TOF should be referred to those individuals and any changes to their settings must be approved by them. Additional experts may be trained by the system owner and their name and date added to this table.

Table: Expert personnel for the TOF system

Name	Extension	Date of qualification
Mark Ito	269-5295	June 12, 2014