Proposal for sac prototype basing on shashlyk technique
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Proposal for SAC prototype basing on “Shashlyk” technique. INR (Moscow), University of Sofia. Basic requirements. The proposal is based on the idea to construct a prototype of SAC as close as possible to the final design. Also “by product” to have identical approach for the IRC.

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Proposal for sac prototype basing on shashlyk technique

Proposal for SAC prototype basing on “Shashlyk” technique

INR (Moscow), University of Sofia

E.Guschin, NA48(3) PhotonVetoes


Basic requirements
Basic requirements

The proposal is based on the idea to construct a prototype of SAC as close as possible to the final design. Also “by product” to have identical approach for the IRC.

Proposed structure and parameters:

  • SAC geometry:

    • active area: 20x20cm2 + shower size = 24-25 cm2

    • Sampling 70 layers of 1.5mm Sci +1.5mm Lead -> X0=12.5mm , R_M=27mm

    • Depth of 18X0 to have “punch through” eff. less than 10^-5 = 22 cm + fiber bundle + read-out

  • WLS fibres : 1mm diameter Y-11(250)MSJ (Kuraray)

  • Pitch between holes is 9.5 mm, hole diameter is ~1.4mm

  • Energy resolution ~7%/sqrt(E) -> σ = 170MeV @ 6GeV

  • Time response is defined by WLS fiber type: Y-11 decay time is 10nsec + signal shaping in the read-out.

  • Light yield estimate is ~9 photons/MeV.

E.Guschin, NA48(3) PhotonVetoes


Shashlyk fine sampling prototypes
Shashlyk fine sampling prototypes

Experience: 1996-97 – Fine sampling Prototypes, INR

Various sampling:

0.35mm(Pb)+1.4mm(Sci); 0.7+1.4 ; 1.5+1.4 ; 1.5 + 3.0 ; 2.0 + 3.0

Measured energy resolution of ~4.5%/Sqrt(E) for prototype n.5

E.Guschin, NA48(3) PhotonVetoes


Mechanical structure
Mechanical structure

  • Conventional mass-production Shashlyk technique is based on molded scintillator (press-form with holes punching) and stamped lead plates.

  • Another approach based on precise machining with hole drilling was also explored (E787, CMS, “spakebab”, DELPHI) .

  • KOPIO – like approach:

  • Molded scintillator with “lego” lock - > precise geometry

  • No “dead” material between modules

  • Mass-production technique

  • Lateral dimensions are 12x12 cm2, it could be used for SAC with lateral segmentation, but it is difficult to fit ring shape of IRC.

  • Therefore another option for SAC prototype is to machine the cast scintillator and lead and to drill holes using high precision numerical machine and/or face-molded jig.

E.Guschin, NA48(3) PhotonVetoes


Mechanical design
Mechanical design

Assembly roads

Al front and

back planes

Scintillator 1.5mm + Lead 1.5mm

Sampling structure

Total weight is ~ 80kg

for 25x25cm2 area and 70 layers

Front view

Al frame support

E.Guschin, NA48(3) PhotonVetoes


Materials
Materials

  • Lead+Sn(4%) alloy plates, 1.5mm thickness

  • Scintillator plates, 1.5mm thickness

  • TYVEK, 0.1mm

  • WLS fibres: Y11(250) MSJ, 1 mm diameter ~ 300 x 60 cm

    +

  • Tools

  • Support

E.Guschin, NA48(3) PhotonVetoes


Time schedule and responsibilities
Time schedule and responsibilities

Market survey (preliminary) for the cast scintillator : StGobain vs Kharkov; the price difference is ~ tens times.

Preliminary sharing of responsibilities:

Lead + jig – Sofia, Scintillator with holes – INR, fibre – exist (?) INR, for others (TYVEK, mechanics, assembly, photo read-out) there are options to be fixed.

Basic idea on time schedule:

  • Mechanical design to be fixed - June

  • Choice of scintillator options – June

  • Production plan to be fixed by end of June

  • Delivery ( of components) to CERN ( and assembly) - September

E.Guschin, NA48(3) PhotonVetoes


Photo read out
Photo read-out

  • For beam test 4 conventional PMT FEU-84 could be used

  • APD read-out is promising option:

    • Compact

    • Magnetic field insensitive

      But:

    • Smaller area: 1x1cm2 HAMAMATSU (CMS like) – 9 read-out channels

    • Charge particle direct ionization ~ 600 ph.el. (800MeV)

    • Stabilization of temperature (1%/degree C) and bias voltage is needed

    • It needs low noise amplifier + gain of 100-200 -> electronic noise <10 MeV/channel is achievable

E.Guschin, NA48(3) PhotonVetoes


Beam test program
Beam test program

  • Energy response for electrons and tagged gammas:

    • resolution

    • Lateral uniformity of the response

    • Effect on the holes vs angle.

    • Light yield

  • “Punch through” probability with (electrons?) gammas. With tagged gammas the set-up could be:

    • > tagged gamma -> veto scintillating counter -> SAC proto -> ECAL module (“shashlyk” or any available with good energy resolution)

  • Test of APD read-out (if ready)

E.Guschin, NA48(3) PhotonVetoes


Backup slides
BACKUP slides

  • Energy resolution

  • Lateral uniformity

  • Tilted holes effect

E.Guschin, NA48(3) PhotonVetoes


Shashlyk fine sampling results
Shashlyk, fine sampling, results

E.Guschin, NA48(3) PhotonVetoes


Lateral uniformity
Lateral uniformity

KOPIO results:

Light collection efficiency drops on the edge by ~10%

Chemical modification of the side edges of scintillator improves uniformity considerably.

E.Guschin, NA48(3) PhotonVetoes


Design proposal for small angle photon vetoes
Design Proposal for Small Angle Photon Vetoes

Requirements:

  • Extra high registration efficiency for gammas larger than 5 GeV (ineff <10^-5)

    -> thickness ~18-20X0

    -> fibre axis is tilted to the beam

    more than 5 mrad

  • Timing better than 100 ps (?) -> light yield larger than 20 photons/MeV is sufficient *)

    *) following the result for KOPIO with 90ps/Sqrt(E) for 55 ph.el./MeV

  • Cell size / no cells, Molier’s radius - ? Occupancy is low?

KOPIO Shashlyk eff. vs beam angle

E.Guschin, NA48(3) PhotonVetoes


Sac structure
SAC structure

Hermeticity

Few solutions: a) continuous layers of lead and scintillator with drilled holes ; b) non projective cracks ; c) with crack shift from layer to layer.

E.Guschin, NA48(3) PhotonVetoes