Anders Ringbom, Anders Axelsson, Mattias Aldener, Tomas Fritioff, Johan Kastlander, Anders Mörtsell

Swedish Defence Research Agency (FOI)

SAUNA III – a major upgrade

Outline

• Scientific reasons to develop the noble gas systems in IMS.

• SAUNA III development:

• Collection and processing

• Detector

• Software

• Summary and Conclusions

Why do we need to develop the NG systems further?

Practical/economic reasons:

● Improve reliability, maintainability and user friendliness

Scientific reasons:

● The PrepCom requirements, set 20 years ago, need an update● Based on the technology available at the time● Background not known at the time● Only based on detection capability

● Need to approach the problem with respect to network verification capability● What is the unique NG signal, and how do we increase our capability to

detect it using the current 40 station network?

Better sensitivity is not the whole story

Current systems, 1kt , 100% release

Maximum achievable with current site configuration. 60% of explosions detected within one week (background not included).Will not improve with more sensitive systems*.

*FOI talk in session T4.1: “A novel approach to assess the verification capability of the network”

The signals we are looking for...

Isotope combination Network background* (95% conf. level)

Network background* (99% conf. level)

133Xe, 133mXe, and 135Xe 0.27% 0.07%133Xe and 135Xe 3.2% 0.98%133Xe and 133mXe 2.7% 0.67%133Xe 35% 28%133Xe and 131mXe 4.4% 1.9%

● Ratios and ATM compatible with time zero given by seismic signal● Other sources excluded

* Based on > 80 000 samples. See FOI poster:“The global radioxenon background – an update” (T2.4).

DPRK1 SAUNA measurement 2006DPRK1 IMS measurement 2006DPRK3 IMS measurement 2013

Potential improvements

Detection capability:

Relevant for all isotopes at remote stations with low background. Important to increase detection capability for 133mXe everywhere.

Measurement uncertainty:

Important for ratio interpretation. Small uncertainties increase ability to exclude scenarios. Ratio quantification increasingly risky close to detection limit

Time resolution:

Higher time resolution improves source location. Increases ability to distinguish explosion signal from background.

Measurement precision is crucial for discrimination

1h24h

~6 years of data (USX75), 4228 samples, 99% conf. level, 30/4228 = 0.7% remaining

Containment time:

Kalinowski 2010 line

SAUNA: 1999 - 2015 SAUNA-OSI-2014

1990-1999: “pre-SAUNA” NG network in Sweden

1999-2000: The Freiburg INGE experiment

SAUNA I - 1999

SAUNA I atSpitsbergen2000-2004

SAUNA II - 2004

Mobile sampling -2006

SAUNA III - 2018

SAUNA III main specifications

SAUNA II SAUNA III

Carrier gas Helium Nitrogen

Air volume/sample 16 m3 36 m3

Stable Xe volume in cell 1.2 ml 3.0 ml

Collection time 12 h 6 h

Air flow 22 SLM 100 SLM

MDC 133Xe / sample, 2 cells 0.3 mBq/m3 ~0.2 mBq/m3

MDC 133Xe / sample, 4 cells - ~0.15 mBq/m3

Sampling oven

Sampling oven

Pump

PLC

XPU

Process ovens

GC

SoH

Archive

PCPC

UPS

SAUNA II

He Detectors

Pumpand PSA

PLC

XPU

POV

GC

SoH

Archive

PCPC

UPS

SAUNA III

Sampling oven

Sampling oven

N Detectors

Sampling and processing*

Pump PSA Sampling

ovenProcess

oven GC

Goal: x10 sXe enrichment, 95% yield

See FOI poster: “Studies of increased air collection capability for SAUNA III”

Sampling and processing

One oven removed

New GC(OSI-type)Sample re-quantifiedafter activity measurement

Pump PSA Sampling

ovenProcess

oven GC

OSI-typesamplingoven :

Beta detector*

● Nitrogen as carrier gas + larger sXe volume => straggling● GEANT calculations to optimize design● Refinement of polishing and coating technique● Goal: all produced cells should have an energy resolution

< 35 keV @ 129 keV electron energy● Four different designs will be tested. First cells produced.

“polished”ΔE=31 keV

“rough”ΔE=54 keV

* See FOI poster “SAUNA III detector development”

electron energy (keV)

Beta detector

Teflon reflectorΔE=35 keV

New reflectormaterialΔE=28 keV

Example of test resultswith in-house manufacturedcells (SAUNA II geometry).

Achieved memory effect < 0.1 %.

Active energy drift control

● Energy scale drift ~1% / °C for NaI● Other sources for energy drift: PM-tubes, HV supply, …● Studies of drift performed● Solution using active compensation will be designed -

most likely the QC source will be used for this purpose.

New operational software

● All user functionality in one software with one GUI

● The system operated as a state machine with different modes

● Diagnostic mode● Calibration mode● Manual mode● Routine mode

Summary and conclusions

● In order to achieve better verification capability using the 40-station IMS NG network, increased measurement precision and time resolution is needed.

● The SAUNA III project address both issues.● The capacity of the sampling system will increase four-fold compared

to SAUNA II.● Nitrogen will be used as carrier gas.● The beta detector will be further developed to improve energy resolution.● Active adjustment of detector energy drift● New operator software is developed, including one single GUI and new

operational modes.● The design is handed over from FOI to manufacturer in December 2016.● According to manufacturer, production can start in 2018.

● The SAUNA concept - operation at ambient temperature - remains.