Ltcc Manual

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Low-Threshold Cherenkov Counter Operations Manual
M. Ungaro, Jefferson Laboratory
ltcc manual.tex – v1.0
January 31, 2017
Abstract
This document provides an overview of the CLAS12 Low-Threshold Cherenkov Counter
(LTCC) and serves as an Operations Manual for the detector. Instructions are provided for
shift workers related to basic steps of operating and monitoring the HV controls, monitoring
the detector system and responding to alarms, and knowing when to contact the on-call
personnel.

Contents
1 LTCC Overview
2 Information for Shift Workers
2.1 Shift Worker Responsibilities . . . . . . . .
2.1.1 Updating the Logbook . . . . . . . .
2.1.2 Contacting LTCC System Personnel
2.1.3 Hall B Alarm Handler . . . . . . . .
2.2 High Voltage Controls . . . . . . . . . . . .

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3 Resetting the IOCs

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4 LTCC Authorized Personnel

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1

LTCC Overview

The CLAS12 spectrometer is built around a six-coil superconducting toroidal magnet that
divides the active detection area into six 60◦ -wide azimuthal sectors. The spectrometer detects
particles between ∼ 5 and ∼ 40 degrees in the Forward Detector system, and between ∼ 40
and ∼ 120 degrees in the Central Detector system.
The LTCC is part of the CLAS12 Forward Detector (see Fig. 1) and it is used for pion/kaon
discrimination. The LTCC consists of 6 identical sectors of lightweight mirrors, light collecting cones, 5” PMTs and magnetic shields. The sectors are filled with C4 F10 gas, providing
pion/kaon discrimination from 3.5 to 9 GeV/c. Each sector contains:
• 108 lightweight mirrors
• 36 Winston Cones
• 36 5” PMT
• 36 magnetic shields

Figure 1: Left: The LTCC sectors installed on the Forward Carriage. The Forward Carriage
is roughly 10 m in diameter. Right: The path of Cherenkov photons to the PMTs.

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Fig. 2 shows the sector naming conventions for the LTCC system, as well as the definitions
of the left and right sides of each sector, a block diagram of the readout electronics for each
PMT and the rack locations for the LTCC VME electronics and HV mainframes. Note that
“South” refers to beam left and “North” to beam right (closer to the Pie Tower).
The HV power supplies for each LTCC sector are CAEN 1527P mainframes outfitted with
positive polarity 24-channel A1535P modules. Each PMT provides two identical outputs. One
is connected to JLab 250 MHz VME flash ADCs (FADC) and the other to JLab VME leading
edge discriminators and CAEN VME TDCs (100 ps LSB CAEN 1190A).
A summary of the LTCC technical parameters is given in Table 1.

Parameter
Mirrors
Support Structure
Elliptical
Hyperbolic
Mirror Coating
Reflectivity
C4 F10 gas
Refraction Index
Transparency
Density
Window Material
PMTs
200
16
Magnetic Shields
Material
Field Attenuation Factor
PID
π/K separation

Design Value
3 Kevlar layers sandwiched with vinyl foam
Length = 6” to 55”, Width = 8” to 11”
Length = 12” to 30”, Width = 8” to 9.25”
Al/M gF2
90% from 250 to 650 nm
1.00134
100% above 220 nm
9.94 Kg/m3
Tedlar/Mylar/Tedlar composite
Photonis XP 4500B
Photonis XP 4500 (Quartz Window)
Eagle AAA: 80% Ni, 4.20% Mo, and 15% Fe
85 Axial, 390 Transverse
3.5 to 9 GeV/c

Table 1: Table of parameters for the LTCC mirrors, gas, PMTs, and their shielding.

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Figure 2: LTCC naming conventions and readout system. Top: each PMT connects two
identical outputs to both FADC and TDC. Bottom: the location of the HV and readout
electronics for each sector.
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2

Information for Shift Workers

2.1

Shift Worker Responsibilities

The shift worker in the Hall B Counting House has the following responsibilities with regard
to the LTCC system:
1. Updating the Hall B electronic logbook with records of problems or system conditions
(see Section 2.1.1).
2. Contacting LTCC system on-call personnel for any problems that are discovered (see
Section 2.1.2).
3. Responding to LTCC system alarms from the Hall B alarm handler (see Section 2.1.3).
4. If necessary, turning on or off the high voltage for the LTCC system using the HV control
interface (see Section 2.2).
2.1.1

Updating the Logbook

The electronic logbook (or e-log) [1] is set up to run on a specified terminal in the Hall B
Counting House. Shift workers are responsible for keeping an up-to-date and accurate record of
any problems or issues concerning the LTCC system. For any questions regarding the logbook,
its usage, or on what is considered to be a “logbook worthy” entry, consult the assigned shift
leader.
2.1.2

Contacting LTCC System Personnel

As a general rule, shift workers should spend no more than 10 to 15 minutes attempting to
solve any problem that arises with the LTCC system. At that point they should contact the
assigned LTCC on-call worker to either provide advice on how to proceed or to address the
problem.
This document is divided into a section for shift workers and LTCC system experts. However, only LTCC system experts (as listed in Section 4) are authorized to make changes to the
LTCC parameter settings, to work on the hardware or electronics, or to modify the DAQ system software. This division between shift worker responsibilities and expert responsibilities is
essential to maintain in order to protect and safeguard the equipment, to ensure data collection
is as efficient as possible, and to minimize down time. If the shift worker has any questions
regarding how to proceed when an issue arises, the shift leader should be consulted.

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2.1.3

Hall B Alarm Handler

The BEAST alarm handler system running in the Counting House monitors the entire Hall B
Slow Controls system. This includes HV and LV systems, gas systems, torus and solenoid
controls, subsystem environment controls (e.g. temperature, humidity), and pulser calibration
systems (among several others). The system runs on a dedicated terminal in the Counting
House. One of the main responsibilities of the shift worker is to respond to alarms from
this system, either by taking corrective action or contacting the appropriate on-call personnel.
Instructions and details on the alarm handler for Hall B are given in Ref. [2].
For the LTCC system, the two elements monitored by the alarm handler are the HV and
gas systems. Any time a channel trips off an alarm will sound. The alarm handler will identify
the specific channel (or channels) that have tripped. These channels can be reset either through
the alarm handler or through the nominal LTCC HV control screens. These channels should
be reset only after ensuring that whatever condition caused the trip (e.g. bad beam conditions)
has been addressed.

2.2

High Voltage Controls

The LTCC HV is controlled through the Hall B CS-Studio suite, which is an Eclipse-based
collection of tools used as an interface to the EPICS Slow Controls system. To start the user
interface on any terminal in the Hall B Counting House, enter the command clascss. Fig. 3(left)
shows the control panel that is launched.

Figure 3: The CS-Studio interface used for the Slow Controls of the CLAS12 detectors and
subsystems. (Left) General CLAS12 interface. (Right) Options for the LTCC system.

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To bring up the LTCC HV controls, click on the “LTCC” button on the subsystem list. This
pops up a sub-menu of all Slow Controls subprograms for the LTCC system (see Fig. 3(right)).
Clicking the mouse on the “LTCC HV” option brings up the HV control interface for the LTCC
system as shown in Fig. 4. This interface allows for HV operations at a number of functionality
levels:
• All channels in the full LTCC system
• All channels in a single LTCC sector
• The left or the right PMTs in a given sector
• A single PMT in the LTCC system

Figure 4: LTCC HV display and control interface.

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For the shift worker the most common operations are:
1. To turn the HV for all system PMTs on or off. This is accomplished by clicking the
button in the upper right corner “HV MENU”. This pops up a sub-menu with the relevant
options.
2. To turn the HV for all PMTs in a single sector on or off. This is accomplished by clicking
on the corresponding sector button at its nose, denoted with the letter S followed by the
sector number. This pops up a sub-menu with the relevant options.
3. To turn the left or right HV for the PMTs in a given sector on or off. This is accomplished
by clicking on either the L or the R buttons near the sector nose. This pops up a sub-menu
with the relevant options as shown in Fig. 5 (right).
4. To turn individual PMTs on or off. This is accomplished by clicking on the segment
representing the channel of interest. Hovering on the detector picture pops up the segment
nomenclature, see Fig. 5 (left). Clicking on the segment brings up a control screen for the
channel of interest as shown in Fig. 6. Clicking on the “Pw” button toggles the channel
HV on and off.

Figure 5: (Left) Hovering on a LTCC segment will display its index. (Right) Clicking on the
L button brings up options for all PMTs on the left of that sector.

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Figure 6: LTCC HV display and control interface for single channel parameters..
If the “Controls” option is selected for a sector or a left/right part of a sector, a “novice”
window is opened as shown in Fig. 7. This window shows the monitored channel voltage and
current (Vmon (V) and Imon (µA)), the channel status (OFF, ON), and the set channel voltage
and current (Vset (V) and Iset (µA)). If desired, shift workers can toggle the HV settings for
single channels on or off through this interface.

Figure 7: LTCC HV novice channel controls screen.

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In the upper left corner of this “Channel Controls” window is a button marked “expert”
that brings up the window shown in Fig. 8. This allows changes to the system settings for the
maximum channel current, maximum channel voltage setting, and the channel HV ramp up
and ramp down rates. Clicking on the “novice” button in the upper left corner toggles between
the expert and novice screens. The expert screen should only be used by the list of authorized
LTCC personnel given in Section 4.

Figure 8: LTCC HV expert channel controls screen.
The HV Control Interface screen (see Fig. 4) also provides a color key to indicate the channel
status:
• HV off - no highlight color (channel color dark green)
• HV on - bright green
• HV ramping up or ramping down - orange
• HV trip - red
• Communication problem - yellow
• Undefined channel status - magenta

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3

Resetting the IOCs

If there is a communication problem present, which typically appears for all PMTs in a given
sector, the usual cause is an issue of communication between the IOC computer and the HV
mainframe. To reboot the IOC for a given sector, click on “IOCs” button on the Slow Controls
panel within the “Subsystems” portion of the interface (see Fig. 3). Fig. 9 (left) shows the
options that appear on the sub-menu that pops up. On this menu, select “HV IOC Health”
to open the control window shown in Fig. 9 (right). Click on the “Reboot” button for the HV
supply that has the IOC communication problem. The reboot will take less than two minutes
to complete and the yellow communication problem channel indicators should all disappear. If
rebooting the IOC does not solve the problems, contact the Slow Controls system expert.

Figure 9: LTCC HV expert channel controls screen.

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4

LTCC Authorized Personnel

Beyond turning on/off the LTCC system HV and monitoring the system scalers, all other
operations and repairs are only to be carried out by the list of authorized personnel shown
in Table 2. The list of authorized personnel for LTCC can only be modified by LTCC Group
Leader.
Name
Maurizio Ungaro
Cole Smith
Sergey Boyarinov
George Jacobs
Nathan Baltzell

Telephone
757-269-7578
757-269-5795
757-269-5902
757-269-5902

email
ungaro@jlab.org
lcsmith@jlab.org
boyarinov@jlab.org
jacobsg@jlab.org
baltzell@jlab.org

Area
LTCC Group Leader
Hardware
DAQ
Gas System
Slow Controls

Table 2: LTCC detector authorized personnel.

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References
[1] Hall B Electronic Logbook: https://logbooks.jlab.org/book/hblog
[2] Hall B BEAST alarm handler:
https://clasweb.jlab.org/wiki/index.php/Slow Control Alarms

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