July 2021

Group Code: EP-ATLASMS-4684/EP/ATLAS

The ATLAS Muon Spectrometer Phase II upgrade

Market Survey

Technical DescriptionGas volumes for the ATLAS Muon Spectrometer

AbstractThis Technical Description concerns the assembly of gas volumes for theATLAS barrel inner (BI) resistive plate chambers (RPC). The Invitation toTender is planned to be issued during the third quarter of 2021.

iiMS-4684/EP/ATLAS

Table of Contents

1. INTRODUCTION........................................................................................................................... 11.1 Introduction to CERN ....................................................................................................................... 11.2 Introduction to the ATLAS experiment and the BI project ............................................................... 12. SCOPE OF THE SUPPLY ............................................................................................................. 32.1 Deliverables and Activities ............................................................................................................... 32.2 Description of components................................................................................................................ 52.2.1 HPL plates......................................................................................................................................... 52.2.2 Other components ............................................................................................................................. 52.3 Deliverables and Activities ............................................................................................................... 72.4 Equipment provided by CERN.......................................................................................................... 82.5 Options .............................................................................................................................................. 83. REQUIREMENTS.......................................................................................................................... 83.1 Technical Requirements .................................................................................................................... 83.1.1 Mechanical properties....................................................................................................................... 83.1.2 Reliability and environmental specifications .................................................................................... 83.1.3 Electrical properties.......................................................................................................................... 93.2 Norms and Standards ........................................................................................................................ 94. PERFORMANCE OF THE CONTRACT.................................................................................... 94.1 Delivery Schedule ............................................................................................................................. 94.2 Acceptance Tests............................................................................................................................... 94.2.1 Acceptance of the HPL plates ........................................................................................................... 94.2.2 Acceptance of the assembled gas gaps.............................................................................................. 95. CONTACT PERSONS AT CERN............................................................................................... 10

1MS-4684/EP/ATLAS

1. INTRODUCTION

1.1 Introduction to CERNCERN, the European Organization for Nuclear Research, is an intergovernmental organizationcomprising Member States1, with its seat in Geneva, Switzerland. Its facilities are located on eitherside of the border between Switzerland and France (https://maps.web.cern.ch/).CERN’s mission is to enable international collaboration in the field of high-energy particle physicsresearch and to this end it designs, builds and operates particle accelerators and the associatedexperimental areas. At present, more than 11 000 scientific users from research institutes all over theworld are using CERN’s installations for their experiments.The accelerator complex at CERN is a succession of machines with increasingly higher energies.Each machine injects the beam into the next one, which takes over to bring the beam to an even higherenergy, and so on. The flagship of this complex is the Large Hadron Collider (LHC) as presented onthe CERN website: http://cern.ch.

1.2 Introduction to the ATLAS experiment and the BI projectATLAS, or A Toroidal LHC ApparatuS (www.atlas.ch) is a particle physics experiment at the LargeHadron Collider (LHC) at CERN. The ATLAS detector is designed and constructed to make newparticle discoveries resulting from head-on collisions of protons produced by the LHC ofextraordinarily high energy. ATLAS will investigate the basic forces that have shaped our Universesince the beginning of time and that will determine its fate. Among the possible discovery candidatesare particles that could explain the origin of mass, confirm the existence of extra dimensions in space,unification of fundamental forces, and evidence of dark matter in our Universe. The ATLAS detectoris located in an underground cavern on the Swiss part of CERN. The experiment is in operation andproduces physics results. The ATLAS collaboration (hereinafter “the collaborating institutes”)involves 3000 scientists from 174 institutions in 38 countries. As part of the future contract, CERNwill delegate several activities to the collaborating institutes, including quality assurance tests andproject coordination.The High-Luminosity upgrade of the LHC (HL-LHC) will provide a luminosity 10 times higher thanthe current LHC. The increased luminosity will result in ten times higher radiation levels and tentimes higher data rates, placing stringent requirements on the design of the tracking detectors at theheart of the experiment. In order to exploit the significantly enhanced physics potential offered by theHL-LHC, the ATLAS experiment needs to be substantially upgraded. ATLAS requires a substantialperformance increase of the muon trigger system, which will have to maintain a high efficiency formuons with pT > 20 GeV while keeping the rate of fake triggers under control. This upgrade willaddress the existing main limitations of the RPC system:

the redundancy of the present RPC system is insufficient; the present geometrical acceptance of the trigger in the barrel is only approximately 80%; the present trigger and readout electronics are not compatible with the requirements of the

ATLAS Phase-II trigger and data acquisition scheme;

1http://home.web.cern.ch/about/member-states; except where stipulated otherwise, the term “Member State(s)”

shall mean full member state(s) of CERN, associate member state(s) of CERN and associate member state(s) in thepre-stage of accession to membership of CERN.

2MS-4684/EP/ATLAS

the present RPC gas mixture consists to a large fraction of gases with a very high globalwarming potential (GWP), and possible restrictions on the use of such gases in the futurewould impact the operation of the present RPC chambers.

Figure 1. Layout of the ATLAS Muon Spectrometer highlighting the new RPC and monitored drift tube (MDT)chambers in the Barrel Inner region.

The overall RPC Phase-II upgrade program addressing these limitations consists of three sub-projects:

The installation of triplets of new-generation RPCs in the inner layer of barrel chambers (BI-RPC), illustrated in Fig. 1. This chamber layer will become the backbone of the barrel triggersystem in Phase II, it will close acceptance holes in the barrel trigger, increase by 50% thenumber of measured track points. The procurement of gas volumes will be a key componentof RPC chambers.

The replacement of the trigger and readout electronics, required to make the RPC systemcompatible with the new Phase-II ATLAS trigger and data acquisition system (TDAQ)scheme. The whole trigger and readout electronics chain of the present RPC chambers,excluding the front-end boards, will be replaced.

The retrofitting with new front-end electronics of a limited and targeted set of Barrel Outer(BO) chambers in the regions with highest rates around || = 1.

3MS-4684/EP/ATLAS

2. SCOPE OF THE SUPPLYCERN intends to place a contract for the assembly of approximately 1000 RPC gas volumes (fromnow on gas volumes), as defined in this Technical Description and in accordance with the criteriadefined in the Qualification Questionnaire.

2.1 Deliverables and ActivitiesThe RPC gas volume is the sensor element of the new RPC chambers which will be used in the BIlayer of the Atlas Muon Spectrometer, see Figure 1. Each BI chamber will contain three independentdetectors each including an RPC gas volume.

These devices are very high-precision assemblies (some components up to 10 m) or components ofvery specific nature.An RPC gas volume is structured as large area parallel plate structure, made of about 1.3 mm thickHigh Pressure Laminate (HPL) electrode plates, enclosing a gaseous layer representing the radiationsensitive target and providing as well signal amplification by means of electronic avalanche process.To this extent, CERN is looking for companies able to assemble gas volumes constituted by twoparallel HPL plates, kept at 1 mm distance with micrometric precision. Key features of the Gasvolumes, further developed in this document, are:

Internal surface smoothness of the electrodes at sub-micrometric level; Electrode plates volume resistivity certified in the range of 1-5*1010 cm; the gas tightness at atmospheric pressure; Electrical insulation up to 10 kV between the two HPL plates and towards the outside of the

volume; Uniformity of the distance between the parallel plates better than 15 m ; The gas volumes will be positioned for more than 10 years in a high radiation background

environment. For this reason CERN will provide the list of accepted material which arecapable to well perform for more than ten years exposed to a dose of about 1 kGy.. The gluesused must ensure the reliability of the assembly;

The form factor is typically rectangular with dimensions in the range of 1.2 m x 2.9 m.

The estimated list of gas volumes form factors is shown in the following table and could be subjectto variations. The total layout consists of 816 gas volumes. Assuming a 5% preproduction and anoverall yield of 92%, the total amount to be produced is estimated in 966 gas volumes.

RPC type BIL-A BIL-B BIL-C BIL-D BIL-K BIL-E BIL-F BIL-G BIL-H BIL-I

Length in x (mm) 640 510 365 600 220 640 540 450 310 370

Length in y (mm) 2750 2750 2750 2750 2750 2380 2380 2300 2100 1850

# of units 216 6 12 6 6 42 6 24 18 6

4MS-4684/EP/ATLAS

RPC type BIL-J BIR-A BIR-B BIR-C BIR-D BIM-A BIM-B BIS-A BIS-B

Length in x (mm) 370 780 1104 735 437 437 495 1096 916

Length in y (mm) 1700 2099 819 1260 1536 1536 1536 1820 1820

# of units 6 12 24 24 12 36 72 48 240

5MS-4684/EP/ATLAS

Figure 2. Overview of gas volume dimensions.

2.2 Description of componentsA gas volume consists of two HPL plates 1.3 mm thick, spaced by polycarbonate pillars as describedin Figure 2. The perimeter must be sealed by a polycarbonate frame which has the function ofmechanical support. The two short sides of the frame host the gas input and output manifolds.Externally the electrodes are coated with a graphite paint, finished with higher conductivity edgesand a silver epoxy glued copper foil pad, needed for the electrical connection. All the external facemust be protected and insulated by a glued PET foil. Internally the RPC must be finished with apolymerized film of linseed oil.

2.2.1 HPL platesThe HPL plates must have the following characteristics:

The thickness must be 1.30 ± 0.05 mm; The linear dimensions tolerance must be ±0.5 mm; The bulk resistivity must be in the range (1-5) x 1010Ωcm, when measured at 20 °C of

temperature and 50% of relative humidity; The plates must only be made of a core of multiple phenolic resin impregnated Kraft paper

sheets, and finished on both sides by single sheet of melamine resin impregnated paper; The pressing iron plates must be rectified and smoothed to micrometric level; Surface quality to be preserved across all the assembly process.

2.2.2 Other components

A graphite layer must be printed on the outer face of the HPL plates and must have a surfaceresistivity of (350 ± 50) kΩ/. A crucial feature of the graphite layer should be the stabilityof the resistivity when the surface is scrubbed with a soft tissue. The printing mask will be

6MS-4684/EP/ATLAS

defined by the technical drawings which will be provided to the contractor. The external longedges of the graphite layer must have a factor 10 higher conductivity.

Two insulating polyethylene terephthalate (PET) sheets of (180 ± 10) µm, must be glued onthe external faces of the electrodes. The nominal glue thickness is in the order of 80 µm. Thetotal thickness of the gas volume must not exceed the stated tolerance (±0.5 mm).

The inner surfaces of the HPL electrodes must be covered by a polymerized linseed oil coatingwith ~1 m uniform thickness applied as linseed oil – Heptane solution. A successfulpolymerization of the linseed oil is guaranteed by a sufficient flushing of the oiled gas volumeswith purified air and checked by a test sample.

The pillars shape will be defined by the technical drawings which will be provided to thecontractor. The pillar thickness is (1.00 ± 0.01) mm and they are arranged on a grid with apitch of (70.0 ± 0.5) mm. The pillars must be glued with a thin glue layer so that the totalthickness of the gas gap is within the stated tolerances. Moreover the glue must not protrudefrom the outer perimeter of the pillar.

The polycarbonate frame shape will be defined in the technical drawings. The frame thickness,like the spacers/pillars, is (1.00 ± 0.01) mm. The frame must be glued uniformly, guaranteeingthe tightness of the gas volume. As in the case of the spacers/pillars, the glue must not protrudefrom the inner perimeter of the polycarbonate frame. The two short sides of the frame hostfour windows each for the gas flushing. The edges of the two long sides of the gas volume aresealed with hot melt to prevent high voltage discharge between the two HPL plates and withthe grounded metal envelop.

The gas distributor is composed by three components:o Two polycarbonate plates 1.00 mm thick;o One polycarbonate extruded profile that closes the gas duct (shape defined by the

technical drawings which will be provided to the contractor).All the parts must be glued together avoiding the glue protrudes the outer perimeter. All thedetails concerning the gas distribution channel are described in Figure 2 and subsequenttechnical drawings.

The high voltage and ground contacts must be made with copper thin foils glued on thegraphite layer by silver epoxy resin. The high voltage wire, 40 cm long, must be soldered tothe copper foils. The wire must have the following features:

o Multi strands conductors;o Voltage Rating of 18 kVDC minimum must be supported;o Insulator material FEP;o Diameter over insulator 1.00 mm.

The glues required to put together the components of the assembly, shall not containflammable components and their radiation tolerance up to the expected values of theexperiment shall be certified. The glues to be used in the assembly must be explicitly approvedby CERN or ATLAS collaborating institutes;

7MS-4684/EP/ATLAS

2.3 Deliverables and ActivitiesThe Supply shall include the following deliverables and activities:The contractor shall:

Purchase all the components described in section 2.2. However, CERN or ATLAScollaborating institutes may reserve the right to provide a fraction of the HPL plates describedin section Error! Reference source not found. directly to the contractor. The HPL platesprocured by the contractor shall pass a specific acceptation process described in section 4.2.1;

Design and manufacture all the necessary tooling required for the assembly; Have suitable space for storage and final certification test of the products (see section 4.2); Produce the prototypes, pre-series and series manufacturing, for a total of approximately 1000

gas volumes according to the following schematic list of procedures provided by CERN: Preparation of the two HPL plates:

graphite painting and HV connections; hot melt gluing of the PET film ;

Integration of the HPL plates: Cleaning of inner surfaces; Gluing of spacers grid on one plate; Gluing of lateral frames; Assembly of the second plate on top; Curing under pressure.

Chamber finishing: Sealing all around with hot melt; Application of protective tape; Oiling the internal surfaces; Application of HV wires;

Provide, for each gas gap batch, traceable fabrication information and the results of qualitychecking measurements, in particular:

Gluing strength test per HPL batch; Graphite sheet resistivity measurement at each printing machine restart; Oil polymerization test at each oiling batch through the visual inspection of a test

sample. Provide a basic set of quality control measurements, mainly mechanical properties, for each

produced gas volume, fabrication information and the results of quality checkingmeasurements3.1.1:

Checks of the envelope dimensions according to the tolerances defined in thisdocument;

Visual inspections results;

8MS-4684/EP/ATLAS

Check results of the correct gluing of the insulating PET foils and the absence of airbubbles covering a surface grater then 2-3 mm2 between the insulating foils and thegraphite layer;

Check results of the gas tightness at an internal pressure about 3 mbar before theapplication of any tape on the gas volume edges. (see section 2.4);

Check results the high voltage insulation; Ensure packing of the Supply according to the procedures defined by CERN or the

collaborating institutes in the technical documentation.

2.4 Equipment provided by CERNCERN and collaborating institutes will provide the instrumentation needed for the test of the gastightness described in section 2.3.

2.5 OptionsCERN will reserve the right to order additional units of the Supply up to 20% additional units withinone year from the completion of the production.

3. REQUIREMENTS

3.1 Technical RequirementsThe Supply must comply with the following parameters and conditions.

3.1.1 Mechanical propertiesThe Supply must comply with the following mechanical properties:

Gas volume dimensions and associated tolerances as shown in the technical drawings that willbe provided by CERN;

Gas tight; Absence of deformations and/or surface roughness of the gas volume.

3.1.2 Reliability and environmental specificationsThe structures will be installed in a radioactive environment. No rework, maintenance or replacementof parts will be possible for the whole duration of the experiment expected to last from 2025 until2035. For that reason, the reliability and environmental specifications are of the upmost importance:

Because the equipment will be irradiated during their lifetime (1 kGy total), all thecomponents and manufacturing procedures must be approved by CERN or the ATLAScollaborating institutes;

Mechanical integrity and tightness of the gas pipe anchoring system must be ensured; Complete polymerization of the linseed oil coating must be performed, certified by specific

test at each coating batch through the visual inspection of the inner surfaces of an oiled dummysample;

Absence of non-polymerized oil within the gas pipe inlet must be ensured;

9MS-4684/EP/ATLAS

Absence of gas leaks or gas bubbles between the graphite layer and the PET insulating sheetmust be guaranteed.

3.1.3 Electrical propertiesTo provide the required electrical environment for the electronics components attached to thestructure, the Supply must comply with the following electrical properties:

No current leakage from the graphite layer and/or high voltage cable to any grounded metalplate in contact with gas volume up to 6.5 kV shall be measured;

Electrical continuity of the graphite layers with the HV connections must be guaranteed andwill be verified by capacity measurement.

3.2 Norms and StandardsThe Supply shall comply with ISO 14253–1: Geometrical Product Specifications (GPS) – Inspectionby measurement of work pieces and measuring; equipment — Part 1: Decision rules for provingconformance or non-conformance with specifications.

4. PERFORMANCE OF THE CONTRACT

4.1 Delivery ScheduleThe Invitation to Tender is intended to be issued during Q3 2021, with a contract award in end of2021. The lowest compliant technically acceptable bidder(s) will be requested to manufacture aprototype of the Supply within around six weeks. The assembly of the pre-production and productiongas volumes must then not take longer than two years, with a first unit to be delivered within eightweeks from reception of the first HPL plate supply.

4.2 Acceptance Tests

4.2.1 Acceptance of the HPL platesOnce the HPL plates procured by the contractor are delivered, it is expected that these are firstchecked and accepted by CERN or a collaborating institute before they can be assembled.

4.2.2 Acceptance of the assembled gas gapsCERN and the collaborating institutes will be responsible of the procurement of the detailed designdrawings, and the complete QA-QC procedures.CERN intends to perform the final acceptance tests at the contractor premises.CERN and collaborating institutes will reserve the right to refuse all the gas volume that will not fulfilall the technical specification criteria or that will not pass the following tests:

1. Gas tightness and volume rigidity check, by measuring the over pressure (with respect to theatmosphere) produced by injecting in a closed gas volume the equivalent of 0.3% of the gascontained in it. The over pressure measured must be in the calibration range provided. Theoverpressure must be stable for at least 5 minutes;

2. Absence of current leak out of the gas volume through the external surface in close contactwith a metallic ground reference, when operated with an HV of 6000 V;

10MS-4684/EP/ATLAS

3. The Volt-amperometric response evaluated with measuring the current absorbed by the gasvolume when fluxed with a gas mixture composed by C2H2F4-C4H10-SF6 in the ratio 95%-4,7%-0,3% must respect the following conditions:

a. Quality of the insulation between the two HPL electrodes (for an applied voltage of 2kV the maximum ohmic current must be 1 µA/m2 at temperature of 20 °C);

b. The maximum total current at 6 kV must be less than 1.5 µA/m2 after the subtractionof the ohmic component extrapolated at 6 kV, at temperature of 20 °C and pressure of1010 mbar.

5. CONTACT PERSONS AT CERNAll commercial and technical correspondence concerning the Market Survey shall be communicatedto the CERN Procurement officer and in copy to the Technical officer. Any communication by or toany other person than the CERN Procurement Service shall not be valid and have no effect.

For Technical Matters

Name/Department/Group Tel Email

Prof. Rinaldo Santonico +393408980391 Rinaldo.santonico@roma2.infn.it

Dr. Giulio Aielli +41754112143 Giulio.Aielli@cern.ch

For Commercial and Administrative Matters

Name/Department/Group Tel Email

Mr Charles Carayon +41 22 766 3328 Charles.Carayon@cern.ch

In case of absence:

Mr Joshua Davison +41 22 766 4458 Joshua.Luke.Davison@cern.ch