ATLAS MUON Spectrometer
Thin Gap Chambers
BB5 Gas System Operation Manual
Issue:
Revision:
Reference:
Last Modified:
Prepared by:
1
2
TGC-001-04
16 January 2004
E. Etzion and G. Mikenberg
ATLAS
Muon End-Cap Trigger Chambers
Flammable Gas System at BB5
1 January 2004
This document may be found at:
http://lep1.tau.ac.il/erez/TGC/TGC-Gas-BB5.pdf
Revision record
Issue
1
1
Revision
1
2
Date
1 January 2004
16 January 2004
-2-
Comments
Version 1
Version 1
ATLAS
Muon End-Cap Trigger Chambers
1
Flammable Gas System at BB5
1 January 2004
Introduction
The document describes the gas system used for operating Thin Gap Chambers
(TGC) at BB5. The TGCs operate with a gas which is a mixture of n-Pentane (45%)
and CO2 (55%). This mixture is produced by flushing CO2 and n-Pentane through an
evaporator system at a minimum temperature of 36 oC and regulated by electronic
mass flow meters. A single heated line carries the gas mixture from the gas building
to the chambers testing room where the gas is split between the tested chambers. A
second heated line returns the mixture to the gas room where the n-Pentane is
recycled and the CO2 is exhausted into the atmosphere. An overview of the system is
shown in figure 1. The system that will be first in use has no recycling and therefore it
will use the direct exhaust line from the test room. The document describes both
systems where section 4 describes the recycling line, where section 7, describes the
system without recycling as is currently implemented.
Figure 1-overview of the gas system
2
Gas Supply
CO2 is provided at an input pressure of 5 bars by pressure controllers on the wall
panel (all pressures are relative to the atmospheric pressure). A 25 litter stainless
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Muon End-Cap Trigger Chambers
Flammable Gas System at BB5
1 January 2004
steel tank serves as a reservoir of liquid n-Pentane in the gas mixing room. NPentane flows into the tank from the n-pentane recycler from the return line of the nPentane pump and an input for refill. The outputs include a line to the electric npentane pump and an exhaust line to the outside that goes through a bubbler with 1
mb overpressure. Each of the elements of the system is connected to the electrical
ground of the building. The n-Pentane is pumped at 1.5 bars via a magnetic coupling
pump to ensure that the n-Pentane flow controller is supplied with liquid at a positive
pressure.
3
Gas Mixing
The mixing rack contains two mass flowmeters (a gas flowmeter for the CO2 and a
liquid flowmeter for the n-Pentane). After entering the mixing system (figure 2) the
pressure of the CO2 is reduced to 1.0 bar. The CO2 flow is regulated and monitored
by an electric mass flow meter, which has a maximum capacity of about 150liter/hour. The CO2 flow rate is displayed on the gas rack panel (figure 3) in the
control room. The flow rate is set by a potentiometer on the front of the control panel.
Figure 6 - CO2 flow in L/hr vs Mass flowmetergives the relation between the
controller readings and the actual flow in liter/hour, at 22 oC and pressure of 977
mbar absolute. In parallel, a manual rotameter system is provided for the CO2 to
allow an extra capacity during purging. A visible flow meter tube is provided to
indicate the flow in both the manual and the automatic systems.
The liquid n-Pentane is controlled by a separate liquid mass flow meter with a range
of 25-500 g/hour. The relation from the controller reading is given in Figure 7 and
Figure 8 (in % to gr/hour and in % to liter/hour respectively).
The n-Penane mass flow meter injects the liquid into an evaporator, a heated
stainless steel container filled with glass beads, where the mixing takes place. The
evaporator ensures evaporation by warming the n-Pentane with a heating tape
controlled by a thermostat, maintained at a minimum of 36 oC. The relationship
between the controller and the temperature in evaporator is given in Figure 9.
A heat exchange unit cools the gas to 17 oC to ensure that the condensation does
not occur downstream. The output mixture is then sent to the testing area via a
heated stainless steel pipe (LP 102). To protect against over pressure should the gas
valves be closed in the testing area, the output line has a bubbler that goes to the
general exhaust. A rotameter and a mass flow meter are provided to control the total
flow rate. Two electro valves (EV1 and EV2) are provided to isolate the gas mixing
system from the gas distribution before the gas leaves. When EV1 is closed EV2 will
open the system to the exhaust. A rotameter allows monitoring the total exhaust flow.
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Muon End-Cap Trigger Chambers
Flammable Gas System at BB5
1 January 2004
The mixing room is temperature controlled and kept at 21 oC (with alarm set to 17 oC).
The room has also a a flammable gas leak detector.
4
Gas distribution in BHA5 test room
The heated LP102 line brings the mixed gas from building 932 to the tested area in
(Figure 4 - Mixed gas input in BHA5. The line is divided to 20 gas channel in the
distribution rack shown on
5
The n-Pentane Recycling System
In this section we describe the return and recycling system. Nevertheless we
currently start the operation without a return and n-Pentane recycling. The system
currently in use is described in section 7.
The return flow through the heated stainless steel gas return line (LP 101) goes to a
silica-gel container that absorbs any water vapor from the gas before it flows to two
stainless steel tubes cooled to -15 oC and -50 oC ( Figure 10). Here the n-Pentane
condenses and flows back into the liquid n-Pentane gas reservoir. The output gas is
then exhausted into the atmosphere. The silica-gel must be regenerated every month.
Two containers are provided in order to continue operation while one is being
regenerated. The containers have a transparent window to allow for controlling the
absorption level of the silica-gel.
A single heated tube of 10 mm diameter conducts the mixed gas into the TGC testing
area. The distribution system is located in the testing area itself. It consists of a
protection bubbler, a split into flow meters that provide the gas to each individual
units and a return bubbler for each line. Several chambers can be chained in serial to
one distribution line allowing testing several chambers at once.
6
CO2 line
In parallel to the mixed gas system there is also a pure CO2 system (line LP 100) that
is used for inert gas flushing around the detectors, as well as flushing specific
detectors. The line provides a CO2 line followed by a pressure regulator. The return
line is exhausted into the atmosphere.
7
System implemented without recycling line
At the beginning we will use a simplified version of the gas system. The mixing is as
was described in previous sections, the gas will be distributed the the chambers in
the test area, but the return line from the distribution board will go directly to the
exhaust in the test room. In order to avoid condensation in the exhaust line the return
line will get also a direct flow of CO2.
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ATLAS
Muon End-Cap Trigger Chambers
Flammable Gas System at BB5
1 January 2004
Figure 2 - The n-Pentane mixing system, In the following we plot the system as it is implemented
without the recycling line as described in section 6.
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Muon End-Cap Trigger Chambers
Flammable Gas System at BB5
1 January 2004
Figure 3 - The Gas mixing rack
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ATLAS
Muon End-Cap Trigger Chambers
Flammable Gas System at BB5
1 January 2004
Figure 4 - Mixed gas input in BHA5
Mix out
bubllers
Mix in
safety
bubllers
Flowmeters –
mix in line
Figure 5 - gas distribution panel, the rack can supply 20 gas channels.
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Muon End-Cap Trigger Chambers
Flammable Gas System at BB5
1 January 2004
Figure 6 - CO2 flow in L/hr vs Mass flowmeter
Figure 7 - n-Penatne flow l/hr vs FM volts
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ATLAS
Muon End-Cap Trigger Chambers
Flammable Gas System at BB5
1 January 2004
Figure 8 - n-Pentane flow in gr/hr vs mass flowmeter %
Figure 9 -mix mass flow meter l/hr
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ATLAS
Muon End-Cap Trigger Chambers
Flammable Gas System at BB5
1 January 2004
Figure 10 - The n-Pentane Recycling system
8
Operating the system
8.1
Running with CO2 only
Switch on the interface box (control room).
Switch on the mass flow controllers.
Open and set the CO2 pressure (1 bar) at the panel on the room neighbors to the
mixing room.
Using the control knob potentiometer in the control room, turn the CO2 flow to its
correct value.
Open a parallel manual rotameter to correct value (on the gas mixing rack).
Open electro valves EV1 and EV2 and start the pump.
Exhaust can be set either to direct exhaust or recycler.
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Muon End-Cap Trigger Chambers
8.2
Flammable Gas System at BB5
1 January 2004
Running with Mixed Gas.
Switch on the interface box (control room).
Switch on the mass flow controllers.
Open and set the CO2 pressure (1 bar) at the panel on the room neighbors to the
mixing room.
Check the CO2 pressure at the panel on the gas mixing rack, the valve should be 1
bar.
Check the level of the n-Pentane – that should be > 1.5 litter.
Using the control potentiometer, turn the CO2 flow to its correct value (control room).
Start heating the evaporator with the controller potentiometer. Set to about 100 W on
the interface box panel.
Start heating constant bath temperature cooler (control room) set to 17 OC.
Wait until the heat indicator lamp is off (about 15 minutes).
Start the n-Pentane pump.
Check the n-Pentane pressure at the panel (on the gas mixing rack) which should be
1.5 bar. If not, drain the various liquid tubes from gas until achieved. Turn the nPentane flow knob potentiometer to correct value (control room).
8.3
Filling n-Pentane
It is necessary when the level of the n-Pentane drops below 0.5 liter. It can be done
only by the SLIMOS while taking out the sniffer head. Take out the extension tube
from the reservoir. Open the door to have fresh air in the room. Fill the tank with the
special canister. At the end return the sniffer head to its place.
8.4
Purge the Gas System (Experts only!!)
Set the system to CO2 only. Stop the n-Pentane pump. Activate the pump to purge
any left liquid. Set liquid mass flowmeter to 3% level, in order to purge any liquid.
After 30 minutes stop the pump and close the liquid mass flow meter. Run the
system on pure CO2 for 12 hours. Empty the reservoir from the liquid n-Pentane.
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ATLAS
Muon End-Cap Trigger Chambers
9
People
9.1
People in charge
Flammable Gas System at BB5
1 January 2004
In case of problem call:
Name
Erez Etzion
Masaya Ishino
George Mikenberge
9.2
Mobile
Phone
160750
163043
160507
email
71153 [email protected]
74524 [email protected]
73384 [email protected]
Safety Officers
Name
TSO
FGSO - ATLAS
FGSO - EP
GLIMOS - EP
DSO - EP
TIS
William ANDREAZZA
Jan GODLEWSKI
Olav ULLALAND
Gianpaolo BENINCASA
Peter SCHILLY
Jonathan GULLEY
Mobile
Phone
email
164128
76464 [email protected]
164927
72609 [email protected]
163342
72928 [email protected]
163540
74278 [email protected]
160940
73314 [email protected]
160890 78526 74860 [email protected]
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