The isobutane supply is in the Gas Handling Shack located outside the
ISAC-1 experimental hall to the east. Before the experiment begins, ask
Philip Lu (x6575) to start isobutane flow and purge the lines that
run to DRAGON. (See also "Targets|Gastarget|Gas shack" section.)
The isobutane supply line ends at a valve (#20) attached to the cable
tray at the DRAGON end-detector station (see Fig.1). Valve #21 is on a return line
which goes back to the shack, where the exhaust gas is vented. Valve 20B
is on a bypass line which allows purging of the long supply and return
lines.
Fig.1 - MV21, MV20.
A. TO PUMP DOWN FROM ATMOSPHERE
Before first pump-down, confirm that the IC is indeed connected to the
T-piece downstream of the Final slit box. The "IC" microswitch should be
closed and IC mode indicated on the EPICS vacuum page. There is a
checklist binder attached to the IC support frame--a new checklist must be
filled out at the start of IC operation and at the end.
Go to the "ED2 to IC" page and ready the roughing pump: turn on RP21, then open PV21.
Select mode: select "Rough" mode in EPICS
Isolate the IC: close valves IV61, VV61, VV71, SV72 and SV73
Connect volumes on either side of thin window: open RV62, SV74
Start slow pump-down: open RV61 (pumps through needle valve)
Complete pump-down: open RV63 (bypasses needle valve) when pressure
CG61 gets below 5 Torr
Check for leaks: close RV61 and watch for pressure rise on CG61. If
rise is greater than 0.2 Torr/minute the source of the leak should be
investigated. Otherwise, re-open RV61. If the IC was on air, it might take a while to get the water vapour out.
Start TP61: with backing pump BP31 on in Normal mode, pump down
roughing line (CG31A) below 100 mTorr; close RV61, RV62 and RV63; open
BV61; turn On TP61; allow TP61 to come up to speed.
B. FILLING THE IC WITH ISOBUTANE
Enable outflow from IC: confirm valve MV21 is open, turn on RP71, wait
10 seconds, close SV74, open SV73
Set the maximum pressure allowed across the window: click on DPG61 in
EPICS and compare value with what is (believed to be) safe for the mylar window.
Change the value if necessary. Note: after EPICS reboot this number will
be changed back to its default value.
Select the mode: choose "Fill" mode in EPICS.
Check that the Mass Flow Controller (black box below the IC) is set to
Auto for channel 1 (Fig.2).
Fig.2 - IC gas flow controls.
Set the PID pressure-difference value: on the "PID" module press
"Index" until the lower display shows "SP1"; press Up or Down arrow key
until the (red) display of setpoint pressure difference reaches the
desired value; press "Enter"; press Index twice to get simultaneous
display of setpoint and actual pressure difference across the window
Start filling: open MV20, open SV72; watch the pressure DPG61 and MFC
flow; when DPG61 reaches 2-3 Torr the MFC should start to close and DPG61
should go no higher than the setpoint (or 7.5 Torr for lower setpoints);
if this doesn't seem to be happening, close SV72. For ultra-thin windows
it may be desirable to put the setpoint to 0.0, causing the MFC to close,
before opening SV72.
When DPG61 has stabilized, check the MFC flow rate. If it is more
than 10% different from 100 cc/min, adjust manual valve MV74 to get a flow
of about 100 cc/min. (no longer applicableNote: the Bertan HV units have been modified
so that they require an OK from EPICS; the Enable HV condition is that
"qtminflow" is greater than 60 cc/min. The status of the HV Enable signal
may be observed by selecting from the EPICS menu "Vacuum|Mode Selection"
and clicking on the DRAINTHVEN box.)
C. DETECTOR IN USE
Select mode: choose "Run" mode in EPICS
Check pressure reading on CG61. It should reach 0.001 Torr if the window is leak tight.
Connect to separator vacuum: close RV61, open IV61; if IG52 trips off,
reset it and turn it back on. Note: When the hybrid detector is operated without gas in the IC, the "Run" mode condition "DRA:FG71 qtminflow" will not be satisfied.
This presently requires bypassing IV61 to open it. Only do this, when you're 100% sure all other interlocks are satisfied and you're an expert. Otherwise, contact a DRAGON expert.
Turn off the roughing pump: close PV21, turn off RP21
At the end of the experiment or if the system will be unattended for
more than 12 hours, empty the IC: close IV61 and SV72, open SV74.
D. VENTING THE IC
Step down with the PID, and put the setpoint to 0.5 Torr before pumping.
Check that residual isobutane has been pumped away via RP21 (CG61 below 1 Torr).
Select mode: choose "Vent" mode in EPICS
Isolate and connect volumes: close SV73, open RV62. If RV61 is open,
close it.
Stop turbopump TP61: turn off TP61, close BV61; expedite spin-down of
TP61 by a quickly-as-possible opening and closing of VV71; observe
pressure at CG61C: when it drops below 0.5 Torr, give another micro-burst
through VV71; repeat until CG61C matches CG61
Vent IC to 1 atmosphere: open VV71. Leave VV71 open to indicate to
the next user that the IC has been vented.
Contact Philip Lu (x6575) and ask to have the flow stopped at
the Gas Shack. Fill out the after-run part of the checklist.
On the floor below the Ion Chamber is a sensor for the flammable gas alarm
system. In the event that a warning is received by Cyclotron Operations
crew, they should inform ISAC Operations who in turn should contact the
DRAGON experimenters. If an alarm is given, the experimenter should go to
the alarm control panel on the east wall of ISAC-1 experimental hall and
determine whether the alarm is from DRAGON.
If it is, the alarm panel
readings should be noted, then the HV turned off the Ion Chamber (Bertan
units) and isobutane pumped out of the IC. If the alarm condition
persists, turn off pump RP71 and close valves MV20 and MV21 (at the cable
tray above DRAGON end detectors). Consult Philip Lu.
The incident should be noted in the DRAGON hardware logbook and the
facility coordinator informed of it.
D. Hutcheon
19 November 2004
5 April 2007 --- Flammable gas monitor picture added
7 May 2008 --- Turbo TP61 turn-on/turn-off
14 June 2017 --- Added Philip Lu as contact, removed Openshaw and Goyette (both retired)
