Gaseous Helium Cooling of a Thin Silicon Pixel Detector for the Mu3e Experiment

Gaseous Helium Cooling of a Thin Silicon Pixel Detector for the Mu3e Experiment

Adrian Herkert

on behalf of the Mu3e collaboration

Institute of Physics Heidelberg University

09.03.2015

The Mu3e Experiment

Search for the decay µ⁺ →e⁺e⁻e⁺

Goal:

• Sensitivity for the branching ratio of 10⁻¹⁶ Requirements:

• High muon decay rates

• High momentum, vertex, and time resolution of the tracking detector

Met by:

• Low material budget in the acceptance region

• Use of HV-MAPS

The Mu3e Experiment

Detector Concept

Target Inner pixel layers

Scintillating f bres

Outer pixel layers Recurl pixel layers

Scintillator tiles

μ Beam

• B = 1 T

• Pixel detector:

4 cylindrical layers of HV-MAPS

• Timing detectors:

• Scintillating fibres (σ_t<1 ns)

• Scintillating tiles (σ_t∼100 ps)

A. Herkert PI Heidelberg Cooling of the Mu3e Detector Page 3

The Pixel Tracker

Optimized for Low Material Budget

• HV-MAPS

• 50µm

• Flexprint

• 25µm Kapton

• 25µm aluminum traces

• Support structure

• 25µm Kapton

→ _X^x

0 ≈0.1 %

Cooling Concept

μBeam

H₂O Cooling H₂O Cooling

FPGAs

Inactive region:

• Water cooling system integrated in beampipe

Acceptance region:

• Gaseous helium cooling (global + local)

Cooling Concept

μBeam

H₂O Cooling H₂O Cooling He

FPGAs

Inactive region:

• Water cooling system integrated in beampipe Acceptance region:

• Gaseous helium cooling (global + local)

A. Herkert PI Heidelberg Cooling of the Mu3e Detector Page 6

Experimental Cooling Tests

Cooling of One Detector Station with Global Gas Flow

Experimental Cooling Tests

Cooling of One Detector Station with Global Air Flow

0 5 10 15 20 25 30 35 40

10 20 30 40 50 60 70 80 90

v= 2.6 m/s v= 2.8 m/s v= 3.0 m/s v= 3.2 m/s v= 3.5 m/s v= 3.7 m/s

∆T [°C]

Position [cm]

P/A = 150 mW/cm^2

A. Herkert PI Heidelberg Cooling of the Mu3e Detector Page 8

Experimental Cooling Tests

Cooling of One Detector Station with Global Helium Flow

Flow channel Helium container

He He

Air H₂O

HO

CFD Simulations

Cooling of One Detector Station with Global Gas Flow

• P/A = 150 mW/cm²

• v = 3 m/s

Air Helium

A. Herkert PI Heidelberg Cooling of the Mu3e Detector Page 10

Cooling of One Detector Station with Global Gas Flow - Summary

20 40 60 80 100 120

∆Tmax[°C]

Air=simulation He=simulation Air=measurement He=measurement Layer=4

P/A===100=mW/cm²

Local Cooling System

• Cooling from both sides simultaneously

• Supplying helium directly to pixel layers of each individual detector station

A. Herkert PI Heidelberg Cooling of the Mu3e Detector Page 12

Local Cooling Tests with Helium

15 20 25 30 35 40 45 50 55

∆TW[°C]

LayerW3Ww/oWlocalWcooling LayerW4Ww/oWlocalWcooling LayerW3Ww/WlocalWcooling LayerW4Ww/WlocalWcooling P/AW=W250WmW/cm^2 v_global=W2.3Wm/s v_local=W20Wm/s

Further Simulations

A. Herkert PI Heidelberg Cooling of the Mu3e Detector Page 14

Summary

• The proposed cooling concept seems to be suitable for the Mu3e experiment

Outlook

• Simulation of the cooling of the full Mu3e detector

• Investigation of potential flow induced vibrations

x/X

for Different Components of One Tracker Layer

Component Tickness [µm] x/X₀ [%]

Support structure 25 0.018

Flex-print 25 0.018

Aluminum traces 12 0.013

HV-MAPS 50 0.053

Adhesive 10 0.003

Full layer 122 0.105

A. Herkert PI Heidelberg Cooling of the Mu3e Detector Page 16