M23 Inner Regions Upgrade with Triple-GEM detectors

M23 Inner Regions Upgrade with Triple-GEM detectors

The XVLGG(Davide, Gianni & Ale)

INFN CagliariLNF FrascatiINFN Roma

the XVLGG (Davide, Gianni & Ale) 2

Introduction

• LHCb upgrade: the current scenario (from FTDR)

• The weak points of the current system

• The triple-GEM proposal

• Preliminary Cost estimate

• Conclusions

11 May 2012


LHCb Upgrade: The Scenario• 40 MHz readout + flexible software-based trigger

• This will allow annual rates x5 (muonic channels) – x10 (hadronic channels),

• LHCb will also become a general-purpose forward detector

• Running conditions:– Luminosity of 1e33 in LoI; but now in FTDR we plan for 2e33… and what about a

safety factor? The central regions of M2 and M3 are hot and could be much hotter than expected (no M1, no PS, no lead, no SPD anymore, splashes inside calorimeter hole, …)

– Beam structure: 25 ns spacing, mu=2-4

– 5 fb-1/year for a 10 years operation

• Muon system needs to perform efficiently and to operate for ~10 years

11 May 2012


The Current Muon System• As reported by Giovanni on March 27th at the Muon General Meeting, “as far as rates are

concerned we are already marginal at 1x1033 but we are definitely out at 2x1033”

• Giovanni suggested to: – “assess more precisely the expected rates in the inner regions”– “study technological solution to cope with the high rates”

• We strongly believe that we cannot go for a marginal detector which seems “just fine” for 2x1033 – we have to use our experience and include a reasonable safety margin… and upgrade the muon detector to be efficient up to ~5x1033

• (A last minute comment: look at the message received this night: doesn’t this mean that we have to look a bit forward w.r.t. initial ideas?)

11 May 2012


The weak points of the inner part of M23

• The muon system was designed to operate at a luminosity of 2x1032 we need to push this limit at least x10, in particular in these central regions

• This is needed because the higher rates will create large dead-time with the current electronics and layout:

muon system inefficiency

• In addition, these higher particle fluxes will:– Possibly create (position dependent) chamber inefficiencies due to

local space-charge effects – Age detectors (much) faster

• We need to carefully address all the above issues

11 May 2012


Dead Time• Estimate of the rates in M23R12 for 2x1033 (from Giovanni’s

extrapolation from data):

• Wire pads

• Cathode pads

• Most irradiated cath. pad

• With the current electronics (~60 ns “analog” dead time) we are limited at 1 MHz/channel. We definitely need a faster FEE (but probably cannot gain much more than a factor ~2 (carioca has a 12 ns peaking time, but a long tail also, could we aim to 25-30 ns?)

• We likely need some more detector granularity (another factor 3÷4?)

11 May 2012


Rate Capability• The rate expected (according to GP estimates) at

2x1033 (with NO safety factor) are:

• MWPC (with 1-mm wire spacing) rate ref. plot

• MWPC starts to feel space-charge effects at rates closer to ~ MHz/cm2

• (since we are using 2 mm pitch MWPC, 1 MHz in the graph corresponds to ~500 kHz for our chambers)

• From GIF MWPC test: 1 MHz/pad, M3R3 pad size 2.7 x 13.5 cm2 max. 30 kHz/cm2 @gain 6x104

G. Charpak et al, Nucl. Instr. and Meth. 124 (1975) 183

1-mm wire spacing

WIRE PADS CATHODE PADS

LOGICAL PADS <Rate>(cath. Pad)

Ratemax(cath. Pad)

M2R1 0.6 x 25 cm2 3.8 x 3.2 cm2 0.6 x 3.2 cm2 270 kHz/cm2

540 kHz/cm2

M2R2 1.3 x 25.3 cm2

7.6 x 6.3 cm2 1.3 x 6.3 cm2 50 kHz/cm2 110 kHz/cm2

M3R1 0.7 x 27.3 cm2


M3R2 1.4 x 27.3 cm2


11 May 2012


Cluster Size• In M2R12 and in M3R1 we have the

highest cluster size in the whole muon detector due to the fact that in these regions we also have the smallest pad size

• From the plot you can see that Triple-GEM detectors used in M1R1 have a cluster size “on tracks” of ~1.3

• Having in these regions a detector with smaller cluster size will definitely be an advantage, although it is difficult to quantify today these effects because of the uncertainties on the trigger/selection scheme that will be used in LHCb_Upgraded

• Requires further investigations…

11 May 2012

(from: “Performance of the LHCb muon system”, v1.0)


Aging• LHCb MWPC were tested at Casaccia (M. Anelli et al., NIM A599 (2009) 171-175)

• MWPC: LHCb materials, 2 mm pitch, 5 mm gas gap, 30 um diameter wires

• Gas was Ar/CO2/CF4 40/40/20, open-loop, flow at ~3 volumes/h

• Gap currents in the range 1-1.5 mA during test

• About 0.4 C/cm were integrated on 2 gaps (1 was the ref., 1 in short @ 0.3C/cm due to a broken wire)

• Chamber show an apparently correct behavior at GIF after the aging test

• Etching of FR4 found at visual inspection

• Above results seem encouraging, however:

– The gas mixture we use today is different from the one used in the test: the LHCb MWPC gas mixture has a reduced etching capability this could lead to insulating deposits in an aged chamber

– M1R2 chamber dismounted need to be analyzed carefully to understand the observed aging phenomena

– We would need to test MWPC up to at least 1C/cm (Giovanni’s estimate), but an accelerated test cannot be performed at rates in excess of (hopefully) 500 kHz/cm2 because the chamber is already operating in a saturated mode, while at lower rates it takes too much time

11 May 2012


A Working Solution• Triple-GEM detectors with pad readout have already been selected to be used in

M1R1 and are operating according to expectations: offline data quality for one of latest run (114436) gives a M1R1 efficiency of 0.9831, as reported by Patrizia de Simone

• Future M2R1/M3R1 rates will be similar (or even higher) than the current M1R1 rates it seems natural to consider this technology for these inner regions

• In the last 10 years, since the M1R1 triple-GEM proposal, these detectors have increased in popularity and have been used successfully in many experiments: they are now cheaper and more reliable thanks to the improvement in GEM fabrication technology

• We experienced in these years of data taking three GEM foils failure:– Optimized detector working point– Improve understanding in discharge mechanism implication in the design– It exist a strong cooperation with TOTEM and RD51: issues are promptly addressed

• This experience allows us to propose with great confidence Triple-GEM detectors

We strongly believe that this detector type is the RIGHT solution for this environment

11 May 2012


Triple-GEM detectors performance• Can stand up to 50 MHz/cm2 [1]

• Aging was demonstrated with M1R1 GEM gas mixture up to 2.2 C/cm2 [2]; after the aging test the detectors showed the expected efficiency and time resolution with only a 15V increase in supply

• [3] also shows no Triple-GEM aging with Ar/CO2 70/30 up to 0.7 C/cm2 with a gain of 10,000 (we routinely operate at ~half this gain, so should be ok up to 1.4 C/cm2)

• Current integrated charge estimate is 40 mC/cm2 per recorded fb-1 in the most irradiated detector of M1R1 (horizontal plane) since M1R1 and M2R1_upgraded have similar particle rates, ready to integrate 50 fb-1 at these rates, which are similar to what we will have in M2R1 in LHCb upgraded

• This technology seems to be already certified for the M23 inner regions operation at the LHCb upgrade!

[1] http://www.infn.it/thesis/PDF/244-Poli%20Lener-laurea.pdf [2] M. Alfonsi et al., IEEE TRANS. NUCL. SCIENCE, vol. 52 (2005) [3] C. Altunbas et al, DESY Aging Workshop (Nov. 2001) Nucl. Instr. and Meth. A J. Benlloch et al, IEEE NS-45(1998)234

11 May 2012


On the Gas MixtureWe plan to use MWPC gas mixture: Ar/CO2/CF4 40/55/5(in red, a guesstimate of the gas performance – to be verified)

11 May 2012


On Time ResolutionBy comparing with previous measurements we published, the MWPC gas mixture should bring the resolution of a single triple-GEM detector gap somewhere close to 6-7 ns rms (to be confirmed experimentally)

From these plots one can see a big improvement in time resolution when increasing CF4 from 0% to 20%, and only a slightly better resolution when increasing it to 40%

We believe that a 5% CF4 gas mixture should have important improvement with respect to Ar/CO2 only

11 May 2012


Efficiency in a 20 ns Window• We are confident that the use of 4 OR-ed gaps will guarantee

the efficiency and the redundancy that the muon detector requires with this new gas mixture - to be checked

11 May 2012


Discharge Probability

The use of a higher-gain gas mixture minimizes the required GEM operating voltage, and by consequence the spark probability

11 May 2012


M23R12 Triple-GEM Proposal• For the upgrade of most irradiated parts of the

muon system, regions M2R12 and M3R1, we propose Triple-GEM detectors as a possible rad-hard technology

• Our proposal is to use 4-gaps Triple-GEM detectors

• These detectors:1. Innovative construction technique, both for GEM foils and

Detector2. Use MWPC gas3. Simplified HV supply (using resistive dividers)4. Anode pad (size of current logical pad, or smaller) readout11 May 2012


GEM Manufacturing• The GEM foils of the first generation of GEM detectors

double-mask technology

• Maximum size of GEM foils is limited to about 40x40 cm2 (alignment issues)

• CERN TS-DEM Workshop (Rui de Oliveira) developed a new manufacturing technique based on a single-mask photo-lithographic process

• (1) starting raw material is a 50 μm kapton foil with a double-side 5 μm copper clad

• (2) photoresist is deposited on both sides; the mask is laid down and exposed to UV

• (3) metal and kapton etching proceed from top side

• (4) bottom side metal is etched using the kapton as mask. Top side metal is preserved with Cathodic Protection technique (-V0 biased with respect to the chemical bath)

• (5) back to kapton etching to get final hole (asymmetric hole shape)

(1)

(2)

(3)

(4)

(5)

11 May 2012


Large-area GEM foilsWith GEM foils, 30x70 cm2 large, realized with single-mask we built a detector (in the framework of R&D for KLOE upgrade), using the LHCb detector construction technique

11 May 2012


New detector assembly scheme (1)

• The upgrade of inner regions of M2 and M3 requires detectors with an active area that ranges from ~30x25 cm2 up to ~30x65 cm2

• For redundancy, each station chamber must be composed of four sensitive gaps; Globally this upgrade will require the construction of about 200 GEMs (spares chambers not included)

• Considering that the typical construction rate of the first generation GEM detectors was of the order 1-2 chamber/week a new design and assembly procedure must be found

• One has to remove every time-consuming steps (gluing, soldering …) while keeping the efficient solution of the foil stretching (that avoids the use of the internal support frame, a very expensive component requiring for a labor-intensive procedure)

Station Region

# chambers / size(w/out spares)

Total GEM foil area

M2R1 48 –> 30x25 cm2 10.8 m2

M2R2 96 –> 60x25 cm2 43.2 m2

M3R1 48–> 32x27 cm2 11 m2

11 May 2012

New detector assembly scheme (2)

• Rui de Oliveira at CERN developed a new detector assembly scheme inspired to our “stretching technique“ of GEM foils ( “embedded-stretching ” technique) that seems suitable for mass-production and possible industrialization (technology transfer) of the whole construction process

• The idea is to re-scale and adapt the design of our stretching tool in order to be embedded inside the detector itself

• With this new technique several 10x10 cm2 and 30 x30 cm2 prototypes have been already built and tested

• We already purchase one “standard” detector and will soon try this technique


The screw is pulling out the internal frame on which GEMs are fixed

Readout PCB

GEMs

Drift Detector Base

internal frame

jaws

external frame

11 May 2012


The GEM foil is produced with a pattern of holes all around its perimeter

11 May 2012


On the drift plane (honeycombed PCB) connection pins for HV distribution to GEM foils & holes for assembly are foreseen

11 May 2012


An external frame is coupled with the cathode plane, all around its perimeter “stretching screws” (4-5 cm pitch) are inserted. An O-ring will ensure the gas tightness.

11 May 2012


The three GEM foils, piled-up one over the other, are coupled by means of 4-5 mm wide internal frames (one for each side of the GEM foil). They act as GEM spacer and clamping the foils allows the stretching of GEMs. Embedded feed-through for supply the HV to each GEM foil are inserted inside special blind holes of frames (not visible in the picture)

Detail of the frames:the GEM “sandwich” isfixed on frames with screws

11 May 2012


Detail of the O-ring

Once the foils are correctly stretched, the readout board can be mounted and fixed with screws, closing the detector. The gas tightness is ensured by plastic O-ring placed on top of the external frame, as well as through each stretching screw

11 May 2012


Assembly Scheme SummaryThe new design of GEMs detector offers many advantages:– No gluing, no soldering during the assembly procedure

– No special tooling required

– The detector does not need a spacer in the active area

– Assembly is very fast and easy (~ 1/day with 2 people crew)

– If needed, the detector can be re-opened for modifications, repairs, or to replace a GEM foil

11 May 2012


Production Cost EstimateM2R1 (48 detectors) (or M3R1)

GEM foil 10.8 m2 x 2000 CHF/1.2 18.000 €/48 det.s = 375 € /det. PCBs (cath.+anode) 200 +576+350+1104 = 2230 €/48 det.s = 50 € /det. Honeycomb+ backplane 80x96 = 7680 €/48 det.s = 160 € /det. Detector mechanics 300 € /det. ___________ total 885 € /det.

TOTAL COST ESTIMATE FOR M2R1 or M3R1 885 x 48 = 42.480 €

M2R2 (96 detectors)

GEM foil 43.2 m2 x 2000 CHF/1.2 72.000 €/96 det.s = 750 € /det. PCBs (cath.+anode) 220+2304+350+4320 = 7194€/96 det.s = 75 € /det. Honeycomb+ backplane 100x192 = 19200€/96 det.s = 200 € /det. Detector mechanics 500 € /det. ____________ total 1525 € /det.

TOTAL COST ESTIMATE FOR M2R2 1525 x 96 = 146.400 €

In green : budgetary offerIn yellow : estimate (in excess) from personal experiences

11 May 2012


Manpower• From FTDR:

– Cagliari: 7 researchers

– LNF: 13 researchers

– Roma: 9 researchers

… for the moment11 May 2012


Tentative Planning• 2012

– Prototype assembly and test – Gas mixture studies

• 2013– Design– Production of one 4-gap triple-GEM detector– Test beam at PSI with CARIOCAGEM

• 2014– Final design– Detector test with new electronics

11 May 2012


Conclusions• The inner regions of M2 and M3 of the current muon detector

cannot be operated with the required performances at 2x1033

• MWPC technology does not seem to guarantee a sufficient operational safety margin if used in M2/M3 inner regions

• GEM foil new fabrication technique is cheap and reliable; together with the proposed detector assembly scheme we can built fast and easily the required chambers

• The total cost of the detectors for M2R12 and M3R1 is ≈250k€

• Triple-GEM detector seems the right choice to equip M2 and M3 inner regions

11 May 2012


Remember, we should never forget this!11 May 2012


Spare Slides

11 May 2012


GEM Aging with Ar/CO2 70/30

11 May 2012

M23 Inner Regions Upgrade with Triple-GEM detectors

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