Task Group 2

Iris Abt, Michael Altmann, Kevin Kroeninger, Bela Majorovits, Franz Stelzer, Xiang Liu

1. Detector Development2. Suspension & Cabling3. MC Simulation4. Outlook & Conclusion

Prototype Test-stands & Crystals

Gerda Collab. , Nov. 9-11, 2005 Page 2

3 test-stands:Milchkanne: LN2Gerdalinchen: LN2Galatea: Vacuum

2 Canberra crystals (n-type)Mikesch-I : non-segmentMikesch-II: 18 segments, 6 x 3z (end of year)

3 DSG crystals (p-type)Roland-I : true coaxial, non-segment Roland-II : 6 segmentsRoland-III: 18 segments, 6 x 3z (end of year)

Gerda Collab. , Nov. 9-11, 2005 Page 3

Mikesch-I

Eurysis

Canberra n-type crystalNon segmentNon-true-coaxial

1st: Milchkanne & Mikesch crystal

Mikesch in LN2

Gerda Collab. , Nov. 9-11, 2005 Page 4

13 LN2 & 1 LAr cooling-warming cyclesFWHM~3.5keV(electronic noise dominated)

Crystal axis affects electron-hole drift velocity

Rise-time vs. crystal angle (241Am)

Mikesch in LAr

Gerda Collab. , Nov. 9-11, 2005 Page 5

In LAr

In LN2

Eu152 spectrum

2nd: Gerdalinchen & DSG Roland-I II

Gerda Collab. , Nov. 9-11, 2005 Page 6

Similar to Gerda setup & environmentMulti-purpose, test suspension stringsMulti-crystals.

IR shielding

2nd: Gerdalinchen & DSG Roland-I II

Gerda Collab. , Nov. 9-11, 2005 Page 7

Roland-I

Roland-II

IR Shield

DSG Roland-I & II performance

Gerda Collab. , Nov. 9-11, 2005 Page 8

Infrared increases leakage current, shielding very important

Roland-I leakage current

A

Roland-II

Roland-II Current (2kV)

No shield 8.4nA

Shield –120°C 120pA

Shield in LN2 55pA V_bias

Suspension system design

Gerda Collab. , Nov. 9-11, 2005 Page 9

Kapton cable

suspensionstring (Cu)

holders (cu, teflon)

bond pads

Cabling tests with optical crystal

Gerda Collab. , Nov. 9-11, 2005 Page 10

Materials & MaGe MC

Gerda Collab. , Nov. 9-11, 2005 Page 11

Cu: Cresst, Gerda, Majorana Majorana Cu stress test: ok for 35kgKapton-cable: pure K, K-Cu, K-Cu-Ni-Au contamination measurement in HADES

Need MC forcontamination limit

MaGe simulation

MaGe simulation results

Gerda Collab. , Nov. 9-11, 2005 Page 12

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MaGe simulation results

Gerda Collab. , Nov. 9-11, 2005 Page 13

68Ge in crystals238U, 232Th in crystals <0.4 Bq/kg210Pb on crystal surface <0.2 Bq/kg238U, 232Th in Kapton cable <2 mBq/kg238U, 232Th in junction box <0.5mBq/kg

Dominant backgrounds:

Upper limit on other materials:

material 238U (mBq/kg) 232Th (mBq/kg)

Cu (holder) 0.4 0.2

Cu (string) 10 10

Teflon (holder) 1.9 1.4

Gerda internal note (GSTR-05-019) ready

3rd Test-stand: Galatea

Gerda Collab. , Nov. 9-11, 2005 Page 14

for laser, & sources

inside Vacuum tank

3 stages for source

Outlook

Gerda Collab. , Nov. 9-11, 2005 Page 15

Milchkanne Test-stand: More cycles, more lAr test

Gerdalinchen Test-stand:Mikesch-II, Roland-I & II & III: resolution, mirror charge, pulse shape, crystal axis

Galatea Vacuum Test-stand: with laser, & sources. all of the above, plus thickness of dead layers

Conclusion

Gerda Collab. , Nov. 9-11, 2005 Page 16

Learned from test-stands:Crystals sensitive to IR radiation (both n,p-types)Need axis orientation of each crystal (for pulse shape)Crystals fragile with water

Learned from MC: Dominant internal background sources located (68Ge in crystal, 238U 232Th in Kapton) Upper limit for all suspension and cabling materials.

Complete prototype design of support & cable for Phase-II available.

Backup: Co60, Ge68, Pb210 contamination

Gerda Collab. , Nov. 9-11, 2005 Page 17

Co60 in crystal: 4/kg/day above ground, assume 10 days above ground, 40 atoms/kg first year, 4.9 decays per kg, 0.16 Bq/kg

Ge68 in crystal: 1/kg day, saturation 400 /kg assume 180 days from enriching to storage undergd., 145/kg 60% decay in first year, 2.7 Bq/kg

Pb210 on surface: 4000 Rn/crystal during installation 45 decays/year/crystal 0.26 Bq/kg

MaGe simulation

Gerda Collab. , Nov. 9-11, 2005 Page 18

Components: Crystal Cu holder Teflon holder Cu suspension string kapton cable bonding pads electronic Junction box

Contaminations:Th232U238Pb210Co60Ge68

Crystal axis effect

Gerda Collab. , Nov. 9-11, 2005 Page 19

Rege

Materials & MaGe MC

Gerda Collab. , Nov. 9-11, 2005 Page 20

Cu: Cresst, Gerda, Majorana Majorana Cu stress test: ok for 35kgKapton-cable: pure K, K-Cu, K-Cu-Ni-Au contamination measurement in HADES

Need MC forcontamination limit

MaGe simulationHolderSuspension stringKapton cableJunction boxcrystals

Mikesch in LAr

Gerda Collab. , Nov. 9-11, 2005 Page 5

In LAr

In LN2

Roland-I pulse shapes & resolution

Gerda Collab. , Nov. 9-11, 2005 Page 21

ns

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