The ModuLAr Project LoI discussion INFN-LNL 21/11/2007 Legnaro (PD)

The MODULAr project The ModuLAr Project pursues a substantial upgrade of a LAr detector for CNGS neutrino beam, having in mind competition and timetable comparable to the ones of NO A at Fermilab for the measurements of θ 13 mixing the mass hierarchy

Why LAr TPC Typical energy spectrum of Neutrinos (Fnal)

e appearance: Background Sources   e contamination in  beam (typically 10%)  Neutral Current interactions of e, misidentified as CC e interaction  + N  +  0 X A rejection of over 99% must be achieved

From ICARUS to MOduLAr The ICARUS T600 experience demonstrates the Lar technology is workable Therefore it represents the right choice for the forthcoming Long Baseline Neutrino Program

Cross Section of one ModuLAr unit

The MODULAr choice Serious arguments suggest the use of a MODULar structure of several identical vessels, each one of the size of a few thousands ton: Overcoming events due to poisoning of the liquid Safety requirements Production of large fluctuations in charge collection over very large volumes due to variations in LAr purity Limited electron drift lengths allow to apply well- established read-out technique

From ICARUS to MODULAr The MODULAr detector will borrow many components from ICARUS: Wire plane configuration Readout electronics and the data acquisition Signal feed-troughs Original technology to withstand temperature changes during detector filling High voltage feed-through and the appropriate noise filtering HYDROSORB/OXYSORB as filters for Ar purification in gas and liquid phases PMT’s to provide a trigger and a t=0 signal High precision purity monitors

The use of perlite insulation Thermal conductivity varies with temperature, density, pressure, and conductivity of the gas which fills the insulation spaces Typical thermal conductivity interval: W m -1 K -1 Estimated specific heat loss: about 3.86 W/m 2 (with nominal thermal conductivity of W m -1 K -1, thickness of 1.5 m)

SLICE

SLICE: a prototype for MODULAr The SLICE cross section is identical to a ModuLAr unit: Sensitive area of 8 x 8 m 2 Pair of three readout planes, one at each side of the gap Central HV plane Maximum drift distance of 4 m Sensitive volume: about 264 m 3 LAr mass: 360 ton (roughly as the T300 detector)

Schematics of the SLICE detector

Slice as a test bed for ModuLAr With SLICE we will gain experience:  Designing, constructing and installing wire chambers, feedthroughs, PMT’s etc  Mantaining and achieving purity in a large vessel  Implementing cold electronics

The construction of SLICE will allow to reach the following targets : a) technical goals Develop all the necessary R&D Establish successful technology transfer b) scientific policy Establish physics collaboration at international level c) physics development Record complete neutrino interactions ( e and  ) Develop event reconstruction and identification Develop physics analysis TARGETS

Main R&D studies for SLICE construction Use of Perlite insulation Initial filling Lar purification New read-out design (due to the 4 m long drift) 200 kV HV will require some not-demanding R&D tests PMT’s optimization in terms of size, wave-shifter deposition and quantum efficency A site for SLICE: –Construction –Operation

Electron lifetime

Thermal insulation SLICE is thermally insulated with Perlite walls: The bottom wall is realized with low conductivity bricks, also about m thick SLICE cold surface: about 350 m 2  total loss: 1.35 kWatt Wall thickness1-1.5 m Total Perlite volume550 m 3 Total Perlite mass expanded density of 60 kg/m 3 33 t

Initial filling Method: repeated flushing of the ultra-pure gas Reasonable goal: surviving gaseous volumetric concentration of Oxygen equivalent of the order of (1 ppm) The volume is cooled down and filled with ultra-pure LAr Relative concentration of O 2 reduced by the obvious factor 1/800, i.e /800 = 1.25 × ≈1.25 ppb Electron lifetime 350 µs Further purification with Oxisorb Final electron lifetime of about 10 ms achieveble (?), corresponding to a 30 ppt Oxygen equivalent (20% attenuation for 4 m drift distance)

The LAr purification Purifiers: set of filters placed outside the perlite vessel and connected with the help of appropriate pumps to the inner LAr volume LAr flow must proceed orderly and uniformly to avoid possible “pockets” of limited circulation To avoid this effect, a bottom containment plate with many small holes uniformly distributed over the whole surface, is under study

Open questions (1) : Vessel  Material (Al or Stainless Steel)  Wall thickness vs safety factors and stiffness  Has the vessel to be opened ? What about perlite?  Is a storage dewar needed?

Open questions (2)  How to obtain constant and stable temperature inside the vessel.  Will the bottom face need superinsulation layers?  Which swimming pool for SLICE?  Are HV feedthroughs a challenge? (200kV or more)

Institutions Bologna LNF LNGS Milano Napoli Padova Pavia Pisa

1 – Main outer dewar with Perlite insulation – Wire planes and other electron signal collecting structures – HV supply to about 200 kV, including race track structures – Light collecting photomultipliers – Initial purification studies without vacuum 60 6 – Readout electronics (6 mm pitch) – Final installation in the test site (CERN) – Contingency and miscellanea 1090 IVA (at 20%) 1308 Total (kEURO) 7848 Cost Estimate

The CERN/GranSasso (CNGS) neutrino complex represents an unique opportunity for neutrinos studies in Europe, concurrent time-wise with T2K and NOvA. The ModuLAr Project

SLICE Structure

Electron Attenuation

Schematics of the SLICE detector