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Low-level techniques applied in experiments looking for rare events
Low-level techniques applied in experiments looking for rare events
1. Introduction
1. Introduction
2. Germanium spectroscopy
2. Germanium spectroscopy
2. Germanium spectroscopy
2. Germanium spectroscopy
2. Germanium spectroscopy
2. Germanium spectroscopy
2. Germanium spectroscopy
2. Germanium spectroscopy
2. Germanium spectroscopy
2. Germanium spectroscopy
3. Radon detection
3. Radon detection
3. Radon detection
3. Radon detection
3. Radon detection
3. Radon detection
3. Radon detection
3. Radon detection
3. Radon detection
3. Radon detection
3. Radon detection
3. Radon detection
3. Radon detection
3. Radon detection
4. Mass spectrometry
4. Mass spectrometry
4. Mass spectrometry
4. Mass spectrometry
4. Mass spectrometry
4. Mass spectrometry
Low-level techniques have “natural” application in experiments looking
Low-level techniques have “natural” application in experiments looking
2. Germanium spectroscopy
2. Germanium spectroscopy

Презентация на тему: «Low-level techniques applied in experiments looking for rare events». Автор: Grzegorz Zuzel. Файл: «Low-level techniques applied in experiments looking for rare events.ppt». Размер zip-архива: 3283 КБ.

Low-level techniques applied in experiments looking for rare events

содержание презентации «Low-level techniques applied in experiments looking for rare events.ppt»
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1 Low-level techniques applied in experiments looking for rare events

Low-level techniques applied in experiments looking for rare events

Grzegorz Zuzel Max Planck Institute for Nuclear Physics, Heidelberg, Germany

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

2 1. Introduction

1. Introduction

Low-level techniques: experimental techniques which allow to investigate very low activities of natural and artificially produced radio-isotopes. material screening (Ge spectroscopy, ICPMS, NA) surface screening (?,?,? spectroscopy) study of radioactive noble gases (emanation, diffusion) purification techniques (gases, liquids) background events rejection techniques modeling of background in experiments (Monte Carlo) Low-level techniques are “naturally” coupled with the experiments looking for rare events (detection of neutrinos, search for dark matter, search for 0?2? decay, search for proton decay, ...), where the backgrounds identification and reduction plays a key role.

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

3 2. Germanium spectroscopy

2. Germanium spectroscopy

Germanium spectroscopy is one of the most powerful techniques to identify ?-emmiters (U/Th chain, 40K, 60Co,...). excellent energy resolution (~ 2 keV) high purity detectors (low intrinsic background)

In order to reach high sensitivity it is necessary: reduce backgrounds originating from external sources - active/passive shielding (underground localizations) - reduction of radon in the sample chamber assure (reasonably) large volumes of samples assure precise calculations/measurements of detection efficiencies

Highly sensitive Ge spectroscopy is a perfect tool for material screening

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

4 2. Germanium spectroscopy

2. Germanium spectroscopy

GeMPIs at GS (3800 m w.e.)

Sensitivity: ~10 ?Bq/kg

GeMPI I operational since 1997 (MPIK) GeMPI II built in 2004 (MCavern) GeMPI III constructed in 2007 (MPIK/LNGS) Worlds most sensitive spectrometers GeMPI I: Crystall: 2.2 kg, ?r = 102 % Bcg. Index (0.1-2.7 MeV): 6840 cts/kg/year Sample chamber: 15 l

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

5 2. Germanium spectroscopy

2. Germanium spectroscopy

Sensitivity: ~1 mBq/kg

Detectors at MPI-K: Dario, Bruno and Corrado

MPI-K LLL: 15 m w.e.

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

6 2. Germanium spectroscopy

2. Germanium spectroscopy

Selected results: different materials

228Th

226Ra

40K

210Pb

Copper

? 0.012

? 0.016

? 0.088

Lead DowRun

? 0.022

? 0.029

0.044 ? 0.014

(27? 4)?103

Ancient lead

? 0.072

? 0.045

? 0.27

? 1300

Teflon

0.023 ? 0.015

0.021 ? 0.009

0.54 ? 0.11

Kapton cable

? 4

9 ? 6

130 ? 60

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

Specific activities in [mBq/kg] G. Heusser et al.

7 2. Germanium spectroscopy

2. Germanium spectroscopy

Selected results: steel for the GERDA cryostat (MPIK/LNGS)

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

8 3. Radon detection

3. Radon detection

Radon 222Rn and its daughters form one of the most dangerous source of background in many experiments inert noble gas belongs to the 238U chain (present in any material) high diffusion and permeability wide range of energy of emitted radiation (with the daughters) surface contaminations with radon daughters (heavy metals) broken equilibrium in the chain at 210Pb level

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

9 3. Radon detection

3. Radon detection

Proportional counters

Developed for the GALLEX/GNO experiment Hand-made at MPI-K (~ 1 cm3 active volume) In case of 222Rn only ?-decays are detected 50 keV threshold - bcg: 0.1 – 2 cpd - total detection efficiency of ~ 1.5 Absolute detection limit ~ 30 µBq (15 atoms)

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

10 3. Radon detection

3. Radon detection

222Rn in gases (N2/Ar) - MoREx

222Rn/226Ra in water - STRAW

222Rn adsorption on activated carbon several AC traps available (MoREx/MoRExino) pre-concentration from 100 – 200 m3 purification is possible (LTA)

222Rn detection limit: ~0.5 ?Bq/m3 (STP) [1 atom in 4 m3]

A combination of 222Rn pre-concentration and low-background counting gives the most sensitive technique for radon detection in gases

Great importance for BOREXINO, GERDA, EXO, XENON, XMASS, WARP, CLEAN, …

222Rn extraction from 350 liters 222Rn and 226Ra measurements possible

222Rn detection limit: ~0.1 mBq/m3 226Ra detection limit: ~0.8 mBq/m3

Production rate: 100 m3/h 222Rn ?0.5 ?Bq/m3 (STP)

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

11 3. Radon detection

3. Radon detection

222Rn emanation and diffusion

Blanks: 20 l ? 50 ?Bq 80 l ? 80 ?Bq

Absolute sensitivity ~100 ?Bq [50 atoms]

Sensitivity ~ 10-13 cm2/s

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

12 3. Radon detection

3. Radon detection

BOREXINO nylon foil

1 ppt U required (~12 ?Bq/kg for 226Ra) Ddry = 2x10-12 cm2/s (ddry= 7 ?m) Dwet = 1x10-9 cm2/s (dwet = 270 ?m) Adry= Asf + 0.14 ? Abulk Awet= Asf +Abulk Separation of the bulk and surface 226Ra conc. was possible through 222Rn emanation Very sensitive technique: (CRa ~ 10 ?Bq/kg)

Bx IV foil: bulk ? 15 ?Bq/kg surface ? 0.8 ?Bq/m2 total = (16 ? 4) ?Bq/kg (1.2 ppt U eqiv.)

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

13 3. Radon detection

3. Radon detection

Online 222Rn monitoring: electrostatic chamber (J. Kiko)

222Rn monitoring in gases Shape adopted to the electrical field Volume: 750 l Sensitivity goal: ~ 50 ?Bq/m3

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

14 3. Radon detection

3. Radon detection

222Rn daughters on surfaces (M. Wojcik)

Screening of 210Po with an alpha spectrometer 50 mm Si-detector, bcg ~ 5 ?/d (1-10 MeV) sensitivity ~ 20 mBq/m2 (100 mBq/kg, 210Po) Screening of 210Bi with a beta spectrometer 2?50 mm Si(Li)-detectors, bcg ~ 0.18/0.40 cpm sensitivity ~ 10 Bq/kg Screening of 210Pb (46.6 keV line) with a gamma spectrometer 25 % - n-type HPGe detector with an active and a passive shield sensitivity ~ 20 Bq/kg Only small samples can be handled – artificial contamination needed: e.g. discs loaded with 222Rn daughters

Copper cleaning tests

Etching removes most of 210Pb and 210Bi (> 98 %) but not 210Po Electropolishing is more effective for all elements but proper conditions have to be found (e.g. 210Po reduction from 30 up to 200) Etching: 1% H2SO4 + 3% H2O2 Electropolishing: 85 % H3PO4 + 5 % 1-butanol

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

15 4. Mass spectrometry

4. Mass spectrometry

Noble gas mass spectrometer

VG 3600 magnetic sector field spectrometer. Used to investigate noble gases in the terrestial and extra-terrestial samples. Adopted to test the nitrogen purity and purification methods.

Detection limits: Ar: 10-9 cm3 Kr: 10-13 cm3

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

16 4. Mass spectrometry

4. Mass spectrometry

Ar and Kr in nitrogen for the BOREXINO experiment (SOL)

Requirements: 222Rn: < 7 ?Bq/m3 39Ar: < 0.5 ?Bq/m3 85Kr: < 0.2 ?Bq/m3 Ar: < 0.4 ppm Kr: < 0.1 ppt

222Rn: 8 ?Bq/m3 Results: Ar: 0.01 ppm Kr: 0.02 ppt

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

17 4. Mass spectrometry

4. Mass spectrometry

Kr in nitrogen: purification tests

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

18 Low-level techniques have “natural” application in experiments looking

Low-level techniques have “natural” application in experiments looking

for rare events. There is a long tradition and a lot of experience at MPI-K in this field (GALLEX/GNO, HDM, BOREXINO, GERDA). Several detectors and experimental methods were developed allowing measurements even at a single atoms level. Some of the developed/applied techniques are world-wide most sensitive (Ge spectroscopy, 222Rn detection). The ”low-level sub-group” is a part of the new division of M. Lindner.

5. Conclusions

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

19 2. Germanium spectroscopy

2. Germanium spectroscopy

Comparison of different detectors

Introduction

Germanium spectroscopy

Radon detection

Mass spectrometry

Conclusions

Slide from M. Hult

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