Module-0 studies for outgassing & cooling

Module-0 studies for outgassing & cooling M.Martini1,2, M.Ricci1,2, G.Pileggi1, B.Ponzio1, S.Miscetti1, F.Happacher1, V.Lollo1, S.Bini1 1LaboratoriNazionali di Frascati 2Università Guglielmo Marconi Roma Meeting with CSN1 referee – La Sapienza - Roma 27 April 2018

Talk layout • Status of outgassing measurements • Calorimeter components • Module 0 • Module 0 “re-assembled” and test in vacuum chamber • Temperature gradient on the crystals • Temperature drops between chiller-pipes-SiPMs • Mechanical structure temperature (Tracker interference)

Status of outgassing measurements • From operation inside the Detector solenoid, the required limit for the outgassing of the whole calorimeter (x2 disks) has been set at 8x10-3Torr liter/s (Docdb# 1481.v5) • This value is 1/10 of the allowed tracker outgassing (that has to deal also with gas • leaks from the straws) in order to make the calorimeter contribution negligible • Our aim is to measure the contribution of the not-standard materials to determine the overall calorimeter outgassing level • These measurements are done using the “known conductance” method:

Status of outgassing measurements • The outgassing values measured so far are summarized in this table: • Full holder means:SiPM+holder+FEE+FC(new measurements with final holders needed) • In addition, we measured contribution from other materials (like G10) to be used as backup solution and also from PTFE plated parts (to reduce friction on calo legs) • To quantify contributions from virtual leaks, we have carried out a parallel measurements campaign with module 0

Module-0 and virtual leaks • The calorimeter Module-0 is composed of 51 (102) • crystals (SiPM/FEE) with full scale/final shape • components and scaled size FEE plate +cooling • lines. • Module 0 has been tested with e- beam @ BTF. • Scaling for the number of crystals/SiPM/FEE and the FEE cooling plate material (Zedex instead of PEEK), Module-0 has the same components of the final calorimeter • With this prototype, we measured the outgassing • of the full matrix and compare with the scaled • contributions of single components (reported in • the previous table) • The difference give us an estimate of the • contribution from virtual leaks

Module-0 and virtual leaks • The difference between the sum of the outgassing of components with module 0, gives virtual leaks • Summing the contribution of each component, we have a total outgassing of 8,1x10-4mbar l/s • This value was pushed by Zedex contribution • The measured outgassing for module 0 was: 1,2x10-3 mbar l/s

Module-0 and virtual leaks • This difference (50%) was due to the structure of the module, not optimized for vacuum • After a deep cleaning and modification of some parts, we repeated this measurement into the new vacuum chamber (next slides) reaching a total outgassing rate of 9x10-4 mbar l/s

Talk layout • Status of outgassing measurements • Calorimeter component • Module 0 • Module 0 “re-assembled” and test in vacuum chamber • Temperature gradient on crystals • Temperature drops between chiller-pipes-SiPMs • Mechanical structure temperature (Tracker interference)

First measurements of Module 0 in vacuum • Module 0 has been re-assembled and installed into the new vacuum chamber built in Frascati(thanks to the Referee support for this!) • This chamber has been built to host both Module 0 and one crate to permit cooling at low temperatures • and is equipped also with a CF windows for beam • and neutrons test. • Our first aims were to use Module 0 to perform the following measurements: • Out-gassing of single components and presence of virtual leaks • Cooling • Heat exchange (both in air and in vacuum) • Grounding • This system will then be used to perform real tests • with cosmics, neutrons and dedicated beams

Temperature gradient • The first test is the measurement of (if any) a temperature gradient along the crystal axis. • This is important to avoid mechanical stresses due to SiPM cooling during run. • To test this effect we installed various PT100 sensors into the module and 5 directly along one selected crystal. • As explained before, in the module 0used at BTF, the front plate was made by a polystyrene foam not usable in vacuum. For this reason: • We substitute it with an aluminum version made in Pisa • We drilled all screws • We performed a deep cleaning and baking of most of the components • This preparation reduced any virtual leaks and allowed us to operate with a good vacuumin the large chamber

Cooling lines The cooling lines inside the chamber have been built using copper pipes that can be used in vacuum. In-out passage and pipes connections were ensured using Swagelok and JIC connectors. The chiller has been filled with a solution of 30% glycol (melting point -13 degrees). [same coolant of the final calorimeter] Cooling line were carefully tested to avoid any liquid leaks.

Connection and readout • Inside the vacuum chamber we haveused (so far): • 1 NIM Mezzanine board to operate • up to 16 SiPM channels • Test beam cables for FEE-Board connection • Ethernet cable to control the Mezzanine board • Signals from the PT100 sensors The chamber has been built to host a final crate with independent cooling line.

Preliminary measurements in air Condition: in air Chiller temperature: 7 degrees Environmental temperature: 23.1 degrees T5= 22.9 OC T5= 22.3 OC T5= 22.1 OC Cylinder: 23.1 OC T5= 21.8 OC T5= 21.3 OC 1.5 OC gradient SiPM: 9.8 OC IN cooling: 7.2 OC OUT cooling: 7.2 OC

Preliminary measurements in vacuum Condition: in vacuum Chiller temperature: 7 degrees Environmental temperature: 22.9 degrees T5= 22.8 OC T5= 22.9 OC T5= 22.8 OC Cylinder: 22.9 OC T5= 22.7 OC T5= 22.4 OC 0.4 OC gradient SiPM: 8.5 OC IN cooling: 6.5 OC OUT cooling: 6.5 OC

Preliminary measurements in vacuum Condition: in vacuum Chiller temperature: 0 degrees Environmental temperature: 22.8 degrees T5= 22.6 OC T5= 22.7 OC T5= 22.5 OC Cylinder: 22.8 OC T5= 22.5 OC T5= 22.0 OC 0.6 OC gradient SiPM: 2.3 OC IN cooling: 1.6 OC OUT cooling: 1.7 OC

First measurement in vacuum at 0 degrees • These first tests permitted to check that the temperature gradient along the crystal axis is • negligible thus confirming ANSYS simulation of • the calorimeter • In this first test the Module 0 was in thermal contact with the vacuum chamber (aluminum on aluminum) Since in the final calorimeter we have an electrical and thermal insulation on the feet made by G10 we used this material to insulate module 0 from the vacuum chamber

First measurement in vacuum at 0 degrees • In the latter configuration • (G10 below Module-0 support) • we want to measure the equilibrium temperature of the mechanical structure. • This is important for the • thermal stability of the tracker (close to the first calo disk)

Chiller conditions for the week long test • 7 days measurement with very stable chiller conditions • Chiller set at -5 to have SiPM temperature close to zero (very similar to the real run conditions)

Mechanical structure temperature • Mechanical structure equilibrium temperature at 9 degrees • Due to vacuum conditions and thermal insulation, day/night effect not visible on aluminum

Crystal gradient • Temperature gradient on crystal constant at 0.5 degrees • Thermal equilibrium between crystals and aluminum structure

Chiller conditions • Measured values confirmed also by ANSYS simulation

Next steps • Substitute aluminum front panel with a CF version produced with the same material of the final calorimeter • (to reproduce/test temperatures distribution close to the • tracker). If needed super-insulation material will be used. • Repeat similar measurements with FEE crate in order to verify temperature distributions • Test calorimeter-crate thermal connection to measure temperature distribution in these regions. • If required by the trackergroup, we could • also modify the legs’ material to keep a • thermal contact while maintaining electrical insulation (ceramic layer) • A first ANSYS simulation confirms • thermal equilibrium in these conditions

Conclusion • The outgassing of most of the detector components has been measured. Some parts to be measured in coming weeks as soon as they will be available (e.g. new SiPM holders, fibers). • Virtual leaks are under control and the total outgassing respect the required limit. • Module 0 has been modified and a long set of thermal measurements have been done. • Temperature gradient on crystals is under control. • Equilibrium temperature of the mechanical structure has been measured. • New measurements will be performed with final crate and module 0+crate • The construction of the vacuum chamber was fundamental to study module 0 response and will be largely used also for other tests (other thermal studies, neutrons irradiation, vertical slice test, etc.)

Module-0 studies for outgassing & cooling