The RPC Closed loop Gas System The RPC Closed loop Gas System

Schedule for completion - update Schedule for completion - update

StatusSupplier: okMixer: okHumidifier: okPurifiers: installed, but not completely commissionedPre-distribution and pump: okFinal distribution: ok (minor detail to fix)Pressure Transmitter on the detector: few sensors are missing

StatusSupplier: okMixer: okHumidifier: okPurifiers: installed, but not completely commissionedPre-distribution and pump: okFinal distribution: ok (minor detail to fix)Pressure Transmitter on the detector: few sensors are missing

Commissioning strategy Commissioning strategy

Phase 0: leak testLeak test of the main pipes form SG to USC and from USC and UXC. Phase 1: debug of circuitIn all racks, the two supply lines for the upper half-wheel and the bottom half-wheel are swapped. Same for the return line. Problem fixed for W+2 and W+1 (the pipe is flexible). For RE+1, RE+2, RE+3 the pipe are rigid and CRIOTEC will fix the problem this week. Also warn to CRIOTEC to avoid the same problem for the negative wheels and endcaps.Flushed for few days with argon the gas distribution racks for W+2, W+1. First check of the flow-cell calibration done.

Phase 0: leak testLeak test of the main pipes form SG to USC and from USC and UXC. Phase 1: debug of circuitIn all racks, the two supply lines for the upper half-wheel and the bottom half-wheel are swapped. Same for the return line. Problem fixed for W+2 and W+1 (the pipe is flexible). For RE+1, RE+2, RE+3 the pipe are rigid and CRIOTEC will fix the problem this week. Also warn to CRIOTEC to avoid the same problem for the negative wheels and endcaps.Flushed for few days with argon the gas distribution racks for W+2, W+1. First check of the flow-cell calibration done.

Phase 2: debug gas rack distributionSystem (up to purifiers, purifiers excluded) flushed with R134a and run in closed loop mode to check both the full system and the flow-cell calibration. At the moment only W+1 rack under test (W+2 and W0 in the the Global Run). As soon as the gas connection in RE+1,+2,+3 are ready we will proceed with these racks. The same will be for W+2 and W0 after the Global Run.

Phase 3: final commissioningInject the RPC mixture and start final commissioning (expected in two weeks). Still some work to be done:•Electrical inspection in SGX5•Detection heads•Close holes between rooms in SGX5 •SGX5 Zone declaration and final ok•Start heating of supply room •Repairs of isobutane and Freon supply panels •IR mixture analyzer still under test (almost ready to be installed)

Finally, RPC operation with high percentage of fresh mixture (from 50% to 30%)

Phase 2: debug gas rack distributionSystem (up to purifiers, purifiers excluded) flushed with R134a and run in closed loop mode to check both the full system and the flow-cell calibration. At the moment only W+1 rack under test (W+2 and W0 in the the Global Run). As soon as the gas connection in RE+1,+2,+3 are ready we will proceed with these racks. The same will be for W+2 and W0 after the Global Run.

Phase 3: final commissioningInject the RPC mixture and start final commissioning (expected in two weeks). Still some work to be done:•Electrical inspection in SGX5•Detection heads•Close holes between rooms in SGX5 •SGX5 Zone declaration and final ok•Start heating of supply room •Repairs of isobutane and Freon supply panels •IR mixture analyzer still under test (almost ready to be installed)

Finally, RPC operation with high percentage of fresh mixture (from 50% to 30%)

Commissioning strategy Commissioning strategy

ISR - Test in progressISR - Test in progress

Open issues•Purification cycle •Effectiveness of the purification•Fresh mixture percentage needed•Stability of the system

Open issues•Purification cycle •Effectiveness of the purification•Fresh mixture percentage needed•Stability of the system

The ISR lab has been converted to a site for the closed loop study

•Few gaps equivalent to 5 RPCs under test with a closed loop prototype system. •10 new Single Gap will be connected this week

•All the detectors are inside a hut with temperature and humidity kept at controlled values

•The mixture composition and quality are continuously monitored by means of a gas chromatograph

•The new gas-chromatograph and mass-spectrometer (CERN Gas Group) will be connected to the pick-up lines this week.

The ISR lab has been converted to a site for the closed loop study

•Few gaps equivalent to 5 RPCs under test with a closed loop prototype system. •10 new Single Gap will be connected this week

•All the detectors are inside a hut with temperature and humidity kept at controlled values

•The mixture composition and quality are continuously monitored by means of a gas chromatograph

•The new gas-chromatograph and mass-spectrometer (CERN Gas Group) will be connected to the pick-up lines this week.

Recent resultsRecent resultsNew cycle started on July 25th

Gas flow: 1 volume/2.5 hGas quality checked every day with a GC

Mixture recycle % injection vs time

System stable for about two month, but now some sign of a small increase in the currents for the gaps operated in closed loop mode

New cycle started on July 25th

Gas flow: 1 volume/2.5 hGas quality checked every day with a GC

Mixture recycle % injection vs time

System stable for about two month, but now some sign of a small increase in the currents for the gaps operated in closed loop mode

(I(t)-I(0))/I(0)open

(I(t)-I(0))/I(0)closed

Recent resultsRecent results

Abnormal “air” level in the mixture (due to R134a cylinder impurity) RPCs switched off

•The “up” gaps are mainly affected by the small increase in the currents.

•Final check (10-15 days in open mode). Then switch again in closed mode with the “old” used purifiers to be sure that the increase is due the their saturation.

•Then regenerate the purifiers and we will start a new cycle (most probably in January).

•The “up” gaps are mainly affected by the small increase in the currents.

•Final check (10-15 days in open mode). Then switch again in closed mode with the “old” used purifiers to be sure that the increase is due the their saturation.

•Then regenerate the purifiers and we will start a new cycle (most probably in January).

More than 13 R134a cylinders analyzed since July 15th with the Gas Chromatograph:

• 6 cylinders < 500 ppm vol “air” • 3 cylinders ~ 4000 ppm vol “air”• 4 cylinders >> 30000 ppm vol “air” (plus an unknown component)

Some example (Gas chromatogram only):

More than 13 R134a cylinders analyzed since July 15th with the Gas Chromatograph:

• 6 cylinders < 500 ppm vol “air” • 3 cylinders ~ 4000 ppm vol “air”• 4 cylinders >> 30000 ppm vol “air” (plus an unknown component)

Some example (Gas chromatogram only):

R134a cylinder impuritiesR134a cylinder impurities

“good” cylinder Very “bad” cylinder

Further analyses will be performed in the next weeks with the GC-MS in order to identify the unknown component (most probably an other kind of freon)

Further analyses will be performed in the next weeks with the GC-MS in order to identify the unknown component (most probably an other kind of freon)

R134a cylinder impuritiesR134a cylinder impurities

Purged volume:“good” cylinder Very “bad” cylinder

0 m3 ~1 m3

Unknown component: ~3 mV ~40 mV

The commissioning of the final gas system is going on

As usual we had/have many problems, but we are confident to start with the final mixture in 1-2 weeks

In the mean time the CMS-RPC gas chromatograph will arrive and will be installed in SG5. Therefore, at the beginning of January, we will start the final commissioning of the purifiers

In the closed loop test at ISR, after about two month of stability the detector currents has shown a small increase. The study is in progress in order to understand if the increase is due to the saturation of the purifiers. The new GC-MS (CERN Gas Group) will be installed at the ISR this week. It will help a lot in the understanding of the purifiers effectiveness.

In one month also the new pH + Fluorine electrode station will be installed first at ISR and then in SG5.

The commissioning of the final gas system is going on

As usual we had/have many problems, but we are confident to start with the final mixture in 1-2 weeks

In the mean time the CMS-RPC gas chromatograph will arrive and will be installed in SG5. Therefore, at the beginning of January, we will start the final commissioning of the purifiers

In the closed loop test at ISR, after about two month of stability the detector currents has shown a small increase. The study is in progress in order to understand if the increase is due to the saturation of the purifiers. The new GC-MS (CERN Gas Group) will be installed at the ISR this week. It will help a lot in the understanding of the purifiers effectiveness.

In one month also the new pH + Fluorine electrode station will be installed first at ISR and then in SG5.

Final remarksFinal remarks

Trigger Top Up

Trigger Top DownClean Mix UpClean Mix Down

Before Mix UpBefore Mix Middle

Before Mix Down

After Mix Down

After Mix UpAfter Mix Middle

Trigger Bottom UpTrigger Bottom Up

START

IN

CAEN Power Supply SY1527

System DAQ

CAEN V96516Channel Dual

Range Multievent QDC

80ns delayeach channel

Fro

nt

end

ele

ctro

nic

s

Low Threshold Discriminators

20ns Delay

Slow ControlVeto

TRIGGER 3/4

Gas gain monitorGas gain monitor

Working at ISRWorking at ISR

Gas gain monitorGas gain monitor

PedestalAvalanche

Streamer

counts

Wheel station sector leak (ml/h) P(0) mbar P(end) mbar Dt (min) leak(mbar/min)W+2 RB3 S03 400 6 3 19 0.158  RB2 S11 3300 6 3 2 1.500  RB3 S11 >14000       n.a.  RB4 S11 >14000       n.a.               W+1 RB3 S05 >14000       n.a.  RB1 S09 >14000       n.a.  RB1 S10 200 6.5 3.5 39 0.077  RB4 S10 5300 6.5 1.7 2 2.400  RB2 S11 >14000       n.a.               W0 RB1 S01 350 4.03 3.5 10 0.050  RB3 S02 1400 4 2 8 0.250  RB3 S08 >14000        n.a               W-1 RB2 S10 >14000       n.a.  RB3 S10 >14000       n.a.               W-2            

System cannot handle the red cases (chamber does not keep any pressure).For the black cases it is possible to compensate the leak with higher flow.

System cannot handle the red cases (chamber does not keep any pressure).For the black cases it is possible to compensate the leak with higher flow.

The “leak” issue: summary The “leak” issue: summary

Wrong operation of gas system:W+2, W+1 chambers have high input pressure due to old impedances valves. To deal with this, the gas rack safety bubbler was changed with a safety valve set to 70 mbar (instead of 10 mbar). Possible source of incident: output of the chamber not properly connected to the rack. However this would not explain cases in W0

Gas pipe damage inside the chamber In one case (chamber already substituted in W-1 due to a large leak), found a

damage pipe inside the chamber. The chambers in W-1 have broken connectors (visible from outside).

Gas pipe agingVery unlikely. Polyethylene pipe used. Aging cases never reported.

Wrong operation of gas system:W+2, W+1 chambers have high input pressure due to old impedances valves. To deal with this, the gas rack safety bubbler was changed with a safety valve set to 70 mbar (instead of 10 mbar). Possible source of incident: output of the chamber not properly connected to the rack. However this would not explain cases in W0

Gas pipe damage inside the chamber In one case (chamber already substituted in W-1 due to a large leak), found a

damage pipe inside the chamber. The chambers in W-1 have broken connectors (visible from outside).

Gas pipe agingVery unlikely. Polyethylene pipe used. Aging cases never reported.

The “leak” issue: possible causes The “leak” issue: possible causes

Leak tests have been performed in all chambers during construction phase, after coupling to DT, before and after installation.

A difference between input and output flow in some cells already observed during MTCC. However the precision of the calibration does not allow to draw conclusions.

Also good performance of the chambers during MTCC and commissioning. This could lead to the conclusion that the leak is at the output.

Leak tests have been performed in all chambers during construction phase, after coupling to DT, before and after installation.

A difference between input and output flow in some cells already observed during MTCC. However the precision of the calibration does not allow to draw conclusions.

Also good performance of the chambers during MTCC and commissioning. This could lead to the conclusion that the leak is at the output.

The “leak” issue: comments and actions The “leak” issue: comments and actions

W+1, W+2 problematic chambers to be opened as soon as possible and replaced with new ones. All chambers ready to be replaced.

W0 one chamber has a serious leak but we try to operate in open mode since no access possible to replace the chamber now.

W+1, W+2 problematic chambers to be opened as soon as possible and replaced with new ones. All chambers ready to be replaced.

W0 one chamber has a serious leak but we try to operate in open mode since no access possible to replace the chamber now.