Optimization of Light Detectors for the CRESST Experiment Anja - - PowerPoint PPT Presentation

▶
optimization of light detectors for the cresst experiment
SMART_READER_LITE
LIVE PREVIEW

Optimization of Light Detectors for the CRESST Experiment Anja - - PowerPoint PPT Presentation

Aug 29, 2023 217 likes •569 views

Optimization of Light Detectors for the CRESST Experiment Anja Tanzke Max-Planck-Institute for Physics Technische Universit at M unchen March 19th 2012 Direct Dark Matter Search with the CRESST Experiment CRESST (Cryogenic Rare Event

slide-1
SLIDE 1

Optimization of Light Detectors for the CRESST Experiment

Anja Tanzke

Max-Planck-Institute for Physics Technische Universit¨ at M¨ unchen

March 19th 2012

slide-2
SLIDE 2

Direct Dark Matter Search with the CRESST Experiment

CRESST (Cryogenic Rare Event Search with Superconducting Thermometers) Direct detection of WIMPs via elastic scattering off nuclei Scintillating CaWO4 crystals as target material Interactions excite phonons and produce scintillation light Scintillation light is used to distinguish different kinds of interactions

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 2 / 15

slide-3
SLIDE 3

CRESST Detector Modules

Phonons signal and light signal are measured

Phonon Channel Light Channel

Signals measured with Transition Edge Sensors (TES) operated at mK temperatures

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 3 / 15

slide-4
SLIDE 4

Light-Phonon-Plane

Coincident light phonon measurement enables event identification

Typical energy resolution

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 4 / 15

slide-5
SLIDE 5

Light-Phonon-Plane

Coincident light phonon measurement enables event identification

Typical energy resolution Light channel energy resolution improved by a factor of 5

Width of the bands is determined by the light channel energy resolution

Goal

Improvement of the light channel’s signal-to-noise ratio

E ∆E

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 4 / 15

slide-6
SLIDE 6

Light Channel’s Signal-to-Noise Ratio

E ∆E depends on many parameters

Measured Energy

E = c · ∂U

∂Φ0 ∂Φ0 ∂I · IT RS+RT · m · r CT · pq · Edep

Noise (@E = 0)

∆E =

  • I 2

J + I 2 SQ + I 2 1/f =

  • 4kB(TC RT +TSRS)

(RT +RS)2

+ c2 + f 2

  • RT

Rn

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 5 / 15

slide-7
SLIDE 7

Light Channel’s Signal-to-Noise Ratio

E ∆E depends on many parameters

Measured Energy

E = c · ∂U

∂Φ0 ∂Φ0 ∂I · IT RS+RT · m · r CT · pq · Edep

Noise (@E = 0)

∆E =

  • I 2

J + I 2 SQ + I 2 1/f =

  • 4kB(TC RT +TSRS)

(RT +RS)2

+ c2 + f 2

  • RT

Rn

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 5 / 15

slide-8
SLIDE 8

Energy Fraction Absorbed by the Light Detector pq

E ∆E ∼ pq (@E = 0)

Data of CRESST Light Detectors

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 6 / 15

slide-9
SLIDE 9

Energy Fraction Absorbed by the Light Detector pq

E ∆E ∼ pq (@E = 0)

Data of CRESST Light Detectors

Increased sensitivity for improved light-production, -transport or

  • absorption
  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 6 / 15

slide-10
SLIDE 10

Energy Fraction Absorbed by the Light Detector pq

E ∆E ∼ pq (@E = 0)

Data of CRESST Light Detectors

Increased sensitivity for improved light-production, -transport or

  • absorption → Black silicon
  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 6 / 15

slide-11
SLIDE 11

Transition Temperature TC

E ∆E ∼ 1 CT ·f (TC ) ∼ 1 TC (1+ε)

Data of CRESST Light Detectors

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 7 / 15

slide-12
SLIDE 12

Transition Temperature TC

E ∆E ∼ 1 CT ·f (TC ) ∼ 1 TC (1+ε)

Data of CRESST Light Detectors

Sensitivity improves for lower transition temperature

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 7 / 15

slide-13
SLIDE 13

Transition Slope m

E ∆E ∼ m = ∆R ∆T

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 8 / 15

slide-14
SLIDE 14

Transition Slope m

E ∆E ∼ m = ∆R ∆T

Transition slope m depends on read-out current Self-heating effect Critical current effect

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 8 / 15

slide-15
SLIDE 15

Transition Slope m

E ∆E ∼ m = ∆R ∆T

Transition slope m depends on read-out current Self-heating effect → ∆TShift =

PT GBT

Critical current effect → expected in the lower part of the transition

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 8 / 15

slide-16
SLIDE 16

Calculation of the Self-Heating Effect

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 9 / 15

slide-17
SLIDE 17

Calculation of the Self-Heating Effect

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 9 / 15

slide-18
SLIDE 18

Calculation of the Self-Heating Effect

Upper part of the transition can be explained with the self-heating effect Difference in the lower part of the transition due to the critical current effect

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 9 / 15

slide-19
SLIDE 19

Reduction of the Normal Conducting Resistance Rn

large Rn small Rn Reduced critical current effect for small Rn

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 10 / 15

slide-20
SLIDE 20

Reduction of the Normal Conducting Resistance Rn

large Rn small Rn Reduced critical current effect for small Rn small Rn opens the possibility for large transition slopes

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 10 / 15

slide-21
SLIDE 21

Thermometer Current IT

E ∆E ∼ IT

9 different light detectors are optimized for best signal-to-noise Limiting factors of thermometer current?

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 11 / 15

slide-22
SLIDE 22

Thermometer Current IT

E ∆E ∼ IT

9 different light detectors are optimized for best signal-to-noise Limiting factors of thermometer current?

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 11 / 15

slide-23
SLIDE 23

Thermometer Current IT

E ∆E ∼ IT

9 different light detectors are optimized for best signal-to-noise Limiting factors of thermometer current? Thermometer current is mostly limited by cooling power

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 11 / 15

slide-24
SLIDE 24

Thermal Coupling between Bath and Thermometer GBT

Increase of IT requires increase of cooling power PBT = GBT(TC − TB) Only possible with larger thermal coupling → Increase of thermal coupling

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 12 / 15

slide-25
SLIDE 25

Thermal Coupling between Bath and Thermometer GBT

Increase of IT requires increase of cooling power PBT = GBT(TC − TB) Only possible with larger thermal coupling → Increase of thermal coupling Temperature rise for given energy deposition reduced with larger thermal coupling → Reduction of thermal coupling

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 12 / 15

slide-26
SLIDE 26

Thermal Coupling between Bath and Thermometer GBT

Increase of IT requires increase of cooling power PBT = GBT(TC − TB) Only possible with larger thermal coupling → Increase of thermal coupling Temperature rise for given energy deposition reduced with larger thermal coupling → Reduction of thermal coupling → Optimization of thermal coupling

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 12 / 15

slide-27
SLIDE 27

Optimization of the Thermal Coupling GBT

Signal height calculated for different thermal couplings Largest signal expected for about ten times larger coupling

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 13 / 15

slide-28
SLIDE 28

Summary and Outlook

Motivation

Light channnel energy resolution is the crucial factor for CRESST

Results

Increase of light-production, -transport or -absorption → Black Silicon Lower transition temperature → Transition temperature of about 15 mK Larger transition slope → Reduction of critical current effect with smaller normal-conducting resistance Increased read-out current with optimized thermal coupling

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 14 / 15

slide-29
SLIDE 29

Thank you for your attention

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 15 / 15

slide-30
SLIDE 30

Backup

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 15 / 15

slide-31
SLIDE 31

Self-Heating Effect

PT = RTI 2

T = RTI 2 Tot R2

S

(RS+RT )2

cooling power: PBT = (TT − TB)GBT → measured ∆TShift = TT − TB =

PT GBT

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 15 / 15

slide-32
SLIDE 32

Critical Current Effect

the thermometer current IT influences the measured resistance the change of the current dIT influences the observed transition → critical current effect is expected to appear for RT RS

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 15 / 15

slide-33
SLIDE 33

Read-out current

IT = ITot

R2

S

RS+RT

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 15 / 15

slide-34
SLIDE 34

Temperature Rise in the Thermometer

∆TT = A+

  • e

− t

τ+ − e

− t

τN

  • +A−
  • e

− t

τ− − e

− t

τN

  • (1)

= A+(t) +A−(t) (2) A± = 1 1 − τN

τ±

· 1

1 τ∓ − 1 τ±

·

  • ε ·

1 τ∓ − GAT + GBT CT

  • + (1 − ε) · GAT

CA

  • · ELD

CT (3) τ± = 2 a ± √ a2 − 4b (4) a = GAT + GBT CT + GAT + GAB CA (5) b = GATGBT + GATGAB + GBTGAB CTCA (6)

  • A. Tanzke (MPP/TUM)

Light Detector Optimization for CRESST March 19th 2012 15 / 15