20.02.14 1

LHCb MUON. Plans on GIF++ (16.65 TBq)

Oleg Maev

What has been done for study of aging in MUON MWPCs and GEMs before RUN1:

- Six months on GIF (137Cs, 675GBq of 662keV) in 2001 – four gap MWPC (prototype) accumulated ~0.255 C/cm of wire and 0.83 C/cm2 of cathodes

- One month on Casaccia Calliope Facility with ~1,25MeV(60Co, ~1015Bq) – four MWPCs and one GEM tested. MWPCs accumulated ~0.44C/cm of wire.

In both tests no gain loss or other significant effect was detected.

20.02.14 2

New requirements on upgraded MUON

Oleg Maev

2008: “LHCb Detector at the LHC” J.Instrum.3 (2008) S08005

At a luminosity of 2x1032 cm2 s-1 the highest rates expected in the inner regions of M1 and M2 are respectively 80 kHz=cm2 and 13 kHz=cm2 per detector plane. In the detector design studies, a safety factor of 2 was applied to the M1 hit multiplicity and the low energy background in stations M2-M5 has been conservatively multiplied by a factor of 5 to account for uncertainties in the simulation.

2013:”LHCb PID Upgrade Technical Design Report”Instantaneous luminosity of 2x1033 cm2 s-1 and for an integrated luminosity of 50 fb-1

Average deposited charge (C/cm of wire) after 50 fb-1 in the most irradiated chamberof each station and region of the muon system.

R1 R2 R3 R4

M2 0.67 0.42 0.1 0.02

M3 0.17 0.08 0.02 0.01

M4 0.22 0.06 0.01 0.004

M5 0.15 0.03 0.01 0.003

At L~2x1032 cm2s-1 ~1C/cm ofwire expected at max. in 10 years- M1 in the detector

At L~2x1033 cm2s-1 ~3C/cm ofwire expected at max. in 10 years (50fb-1)- M1 removed

20.02.14 3

Plans (very preliminary)

Oleg Maev

In order of priority:1. Aging study with set of chambers from inner regions and probably with couple of

chambers from outer regions in shadow – approximately 3-4 months on GIF++ in 2015.2. Some aging study would be desirable with prototypes of high granularity detectors (new

MWPCs and new GEMs) which are under design now for LS2-LS3. It depends on readiness of prototypes. Apparently, it could happened not early than in second half of 2015.

3. As a byproduct study it would be very interest to investigate on GIF++ a method for curing MUON chambers suffered with Malter currents by adding a small amount of oxygen (~0.2-2%) in the nominal Ar(40%)/CO2(55%)/CF4(5%) gas mixture with reverse polarity (negative) and at nominal HV.

See first results in https://indico.cern.ch/getFile.py/access?contribId=3&resId=1&materialId=slides&confId=289760

It could be organized in shadow of 1.

- optimizing the percentage of oxygen in gas mixture- test the method on number chambers suffered with Malter-currents to prove it even

statistically.

20.02.14 4

Infrastructure

Oleg Maev

Aging:1. Gas: MWPCs – nominal mixture:Ar(40%)/CO2(55%)/CF4(5%) 2- 10 l/h GEM – nominal mixture: Ar(45%)/CO2(15%)/CF4(40%) 10-15 l/h - for GEM the mixture potentially could be changed a bit with reducing of CF4

2. HV: MWPCs – CAEN SY2527 GEM – INFN’s PS3. Environment, monitoring atm P,T, H

Malter-currents study:

In general, infrastructure same as for aging, just a couple of additional options:1. Option for admixing a few percent (0,2 -5%) of oxygen2. Very likely a picoampermeter and precise flow mass controller would be

needed

20.02.14 5

News from GIF++ meeting

Oleg Maev

Schedule

612/02/2014A. Fabich, EN-MEF-LE

EDMS 1328252 V0.3

Functional specs:

-Juli 2013

Functional specs:

-Juli 2013 Design-Dec. 2013

Design-Dec. 2013

CE startJan. 2014CE start

Jan. 2014

Infrastructure installation

March-July 2014

Infrastructure installation

March-July 2014Irradiator delivery

Aug. 2014

Irradiator delivery

Aug. 2014

Commissioning Sept.-Oct. 2014Commissioning Sept.-Oct. 2014

Mid May: ready for PH equipment in gas zone

Beginning June: ready for lower muon tracker

Beginning July: ready for PH/users’ equipment in bunker

Decommissioning in the West Area

March: removal of blocks upstream of GIF (no impact on operation)

August/September: secure irradiator

Autumn 2014: removal of infrastructure and concrete castle (SBA)

GIF++ layout (1)

712/02/2014A. Fabich, EN-MEF-LE

dump

secondary beam

PPE (entrance)

MAD

PPG

PPX (only emergency)

dump

service zone

Preparation zone

cable trays to control room

Irradiation area

Service zone: gas (mixing) zone

8

Supply lines for 15 gases simultaneously

40 m2 net area

8 distribution panels with each 6 return lines

17 racks for gas equipment

6 km of piping (304L / 316L)

12/02/2014A. Fabich, EN-MEF-LE

Irradiator

9

hosting a 137 Caesium source: 14 TBq

Irradiator will be equipped with a identical filter system on both sides (up- and down-stream)

30/1/2014

A. Fabich, EN-MEF-LE

DCS ReminderUse PVSS/WinCC OA (as in LHC experiments)

Many components, devices, HW and SW already available (CAEN System, CAN PSU, ELMB, ENV Sensors, VME crates etc.)

CAEN Easy Power System

1 mainframe, 1 Power Generator, 1-2 crates + with HV and LV boards(*) and 1 ADC A-3801 board for monitoring (128 channels), this includes also ENV and gas monitoring

(*) Some Low Voltage possibly external (non CAEN) with remote control via PVSS

Mainframe and PCs possibly placed proximity of the control room (non radiation area) along with DAQ PCs and equipment.

EASY crates and other equipment, more close to detector area.

10A. Polini

10

Mainframe

OP

C

BranchControllers HV/LV Boards

Crate1 Crate2

…

AC/DC converter

48V 48V

…

Hostile Area

Counting Room

A. Polini

Gif++ CERN February 12th 2014 A. Polini

20.02.14 Oleg Maev

20.02.14 12

Preliminary conclusions

Oleg Maev

1. In overall, infrastructure provided by GIF++ facility looks quite good for an

aging test of muon chambers.2. Looks reasonable to use own cables and HV PSs.3. Number of gas mixers and distributors allows to plan most of work and

even studies for MUON, but oxygen for Malter-study4. Proposed strategy: to be ready for an aging test of existing chambers and

prototypes of high granularity detectors before second half of 20155. Some program for Malter-current study in shadow of aging test would be

desirable.6. During preparation of this test, it would be good to continue Malter study in

the PIT this year.7. For the control of aging test on GIF++ a WINCC OA – project would be

useful.8. Involving additional manpower for 2015 is needed.9. Problem – visit’s money for this year at least.

20.02.14 13

Backup

Oleg Maev

20.02.14 Oleg Maev

Malter effect SOURCES:

Avalanche producing polymers deposits

Some oxides are highly resistive.

Constructions material and gas pollutants.

Insulating deposits left from sparks.

Corona on sharp point on the cathode.

Fingerprints

Etc. Ignition mechanisms:

a) Highly ionizing heavy ions.

b) X-rays.

c) Sparks.

d) Sharp points on electrodes causing corona.

Necessary condition for electron emission:a) Localized primary ionization deposit.b) An insulator on the cathode.c) A rate of the charge build up is higher than its removal rate.d) Excessive field cathode gradients help to trigger it.e) To start the effect, it needs an ignition.

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20.02.14 Oleg Maev

“Good” additive – OxygenOxygen ionization reactions in avalanche:

e-+ O2→ O2+ +2e-

e-+ O2→ 2O* + e-

e-+ O2→ O2-

e-+ O2→ e- + O+ + O-

It well known in the Plasma Chemistry that the oxygen radicals and ions excellent reacts with organic compounds and the end product of this reaction are volatile molecules such as CO, CO2, H2O, H2 etc. which are most stable,

and can be removed by gas flow

Practical examples:

The rate of removal of organic polymeric material can be often increased in an oxygen plasma (H. Boeing, Plasma Sci.&Tech., page 281) 1987.

Cleaning of mirrors of the contaminating films by a glow discharge in oxygen plasma. (R. Gillette et al., Vac. Sci. Tech., 7 (1070) 534)

Recovery from the Malter effect deposits by Oxygen (A. Boyarski – BaBar R&D study) 2001.

15

Inverted HV

20.02.14 Oleg Maev

Scanning the CMB with radioactive sources

Scanning with Sr90 - J~70 nA/cm2 ignited the Malter current in two places in GAP A

Scanning with source Am241

(J~0.3 nA/cm2) - no visible effect

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Beam in 2012:

J~0.1 nA/cm2