# Presentation: 626214

## Direct Detection
 of Dark Matter:
CDMS and COUPP

Andrew Sonnenschein

** ****of Dark Matter:**
**CDMS and COUPP**
**Andrew Sonnenschein**

## CDMS Collaboration at Soudan

_*DOE Laboratory*_
**Fermilab**
- LBNL
_*DOE University*_
- Brown
- CalTech
- Florida
- Minnesota
- MIT
- Stanford
- UC Santa Barbara
_*NSF*_
- Case Western Reserve
- Colorado (Denver)
- Santa Clara
- UC Berkeley
_*Canada*_
- Queens

- CDMS and COUPP

- September 26, 2007

## CDMS-II Detectors

- Direct detection of WIMP signal
- Nuclei recoil by elastic scattering
- Read both phonon signal (4 channels) and ionization signal (inner and outer electrode)
- 1cm thick, 7.8 cm diameter
- 250g Germanium, 100g Silicon

**Phonon signal**
**From a quadrant**

**Charge signal**
**From inner electrode**** **

- Phonon signal from
- one quadrant

- CDMS and COUPP

- September 26, 2007

## CDMS Subsystems

- _Shielding_
- Layered shielding (Cu, Pb, polyethylene) reduces radioactive backgrounds and active scintillator veto is >99.9% efficient against cosmic rays.

- _Cryogenics_ Maintain detectors at 50 mK

- _Detectors_
- Ge and Si crystals, 6/tower
- Measure ionization and phonons

- _Electronics/DAQ_
- Record signals from detectors and veto; form trigger

**CDMS Subsystems**

- x5

- CDMS and COUPP

- September 26, 2007

## CDMS II Ongoing Run

- CDMS and COUPP

- September 26, 2007

## SuperCDMS 25 kg

**SuperCDMS 25 kg**

**Proposed 25-kg experiment based on updated 42 x 600-g Ge ZIPs**
**120x beyond current limits**
**15x beyond CDMS-II goal**
**Approved for space at SNOLAB **
**Next step towards ton-scale goal**
**Detector fabrication and characterization underway**
**Detectors have 3x fiducial volume of CDMS-II design.**
**Cost per kg reduced to ****~1/3****.**

- CDMS and COUPP

- September 26, 2007

**Notes:**
4x - rejection (H-si; phonon converage)
2x - analysis
5x - bkg reduction (thickness; as clean as cleanest)
->40x, but need only 20x

## Fermilab responsibilities

**Established roles in CDMS**
- Project Management
- Operations
**Lead the Soudan operations**
- Cryogenics
**Design, construction  of the cryogenics systems**
- Electronics, DAQ, Computing
**Warm electronics, event builder software, online and offline processing**
- Infrastructure
**Clean rooms, control rooms, computing rooms**
- Analysis
**Independent analysis chain**

**New roles for SuperCDMS**
**Backgrounds**
**Collaborating with COUPP on understanding Radon, alpha screening**
**Shield/Veto**
**Do mechanical design and construction together with cryogenics**
**Detectors**
**Exploring possibilities for automated inspection and repair at SiDet**
**May also get involved in bonding our sensors to larger crystals**
**Systems Test**
**Put everything together at Fermilab and test before taking to SNOLAB**
- Need more scientist and engineering help to push forward these new areas

- CDMS and COUPP

- September 26, 2007

## SuperCDMS Cryogenics Design

**Cryogen-free dilution refrigerator**
**Much lower operations and maintenance cost**
**Larger volume to accommodate more detectors**
**More robust thermal connections than in CDMS II**

- CDMS and COUPP

- September 26, 2007

## Progress on SuperCDMS

**Pulse tube cryocooler under test in clean room in Lab 3 at Fermilab**

- New warm electronics prototype for SuperCDMS
- Replaces a chain of four 9U-sized boards used for CDMS II
- Fewer connections, lower power draw => more robust

- CDMS and COUPP

- September 26, 2007

**SuperCDMS Sensitivity**

- CDMS and COUPP

- September 26, 2007

## Dark Matter in Bubble Chambers

- heavy
- target
- nucleus
- e.g. 127I

- 

- Nuclear recoil
-   E ~ 1-100 keV

- Recoil range < 1 micron
- in a liquid, so the signal is a single bubble rather than a track.

- _Measure the rate at which single bubbles appear_

- WIMP

## COUPP: Dark Matter Detection with Bubble Chambers 

**COUPP: Dark Matter Detection with Bubble Chambers **

**Muon**

**WIMP?**

## Principal Investigator:
   Juan Collar
	 (spokesperson)

Graduate Students:
    Nathan Riley
    Matthew Szydagis

Undergraduates:
    Luke Goetzke
    Hannes   
         Schimmelpfennig

KICP Fellows:
   Brian Odom

**Wilson Fellows:**
**	****Andrew Sonnenschein**
**Staff Scientists:**
**	****Peter Cooper**
**	****Mike Crisler**
**	****Martin Hu**
**	****Erik Ramberg**
**	****Bob Tschirhart**

- Principal Investigator:
-    Juan Collar
- 	 (spokesperson)
- Graduate Students:
-     Nathan Riley
-     Matthew Szydagis
- Undergraduates:
-     Luke Goetzke
-     Hannes
-          Schimmelpfennig
- KICP Fellows:
-    Brian Odom

**The COUPP Team**

**University of Chicago**

**National Science Foundation**
**Kavli Institute for Cosmological Physics**
**Department of Energy**

**Funding**

**Fermi National Accelerator**
**             ****Laboratory**

**Principal Investigator:**
**   ****Ilan Levine**
**Undergraduates:**
**   ****Earl Neeley**
**   ****Tina Marie Shepherd**
**Engineers:**
**   ****Ed Behnke**

**Indiana University**
**    ****South Bend**

- CDMS and COUPP

- September 26, 2007

## 1-Liter Chamber in NuMi Tunnel

- Design concept:

## A Typical COUPP Event

**Appearance of a bubble causes the chamber to be triggered.**
**Bubble positions are measured in three dimensions from stereo camera views**

## Spatial Distribution of Bubbles

**Two populations: **
** ****Walls: apparently from radium contamination of quartz.**
** ****Bulk: radon dissolved in chamber liquid**
** **

## Data from 2006 Run

**First physics results were shown at Fermilab last week.**
**Data from pressure scan at two temperatures:**
** **

_**Solid lines:**_
**Expected WIMP response for ******
******SD(p)****=3**** pb**

- Radon
- background

- Energy Threshold
- In KeV

- CDMS and COUPP

- September 26, 2007

## Results from 2006 Run

**We have competitive sensitivity for spin-dependent scattering, despite high radon background**** **

- Spin-dependent

- Spin-independent

- CDMS and COUPP

- September 26, 2007

## New Low-Background Vessel

-  Teflon-coated inconel seals replace Viton.
- Radon emanation <1% of previous design
-  Quartz etched with HF acid by vendor to remove implanted radon daughters.
-   All parts cleaned and assembled in Accelerator Division RF cavity cleaning facility.
-  Very high purity, well-studied water from Sudbury Neutrino Observatory.
-  Bellows made using non-thoriated welding electrodes.

## New Run of 1-liter Chamber

**Inner vessel has been entirely rebuilt with materials believed to have lower radioactivity.**
**New run started July 30, 2007.**
** ****Some radon introduced during filling, now decaying to equilibrium.**

## COUPP 60 Kg Chamber 

**Construction of 60 kg chamber approved by the PAC and director in Fall, 2006. Now being built.**