Centre de Cultura Contemporània de Barcelona 18-22 March 2013

A prototype of a portable TDCR system at ENEA

Marco Capogni, Pierino De Felice ENEA – National Institute of Ionizing Radiation Metrology (INMRI)

Casaccia Research Center Anguillarese street, 301

I-00100 Rome (Italy) marco.capogni@enea.it

LSC 2013 Advances in Liquid Scintillation Spectrometry

OUTLINE

• TDCR technique and the new ENEA TDCR portable instrument

for radioactivity measurements in-situ

• DPP technology in the field of precise measurements of the

radioactivity with Liquid Scintillators

• TDCR analysis within CERN ROOT framework

• Application to the 63Ni and 99Tc activity measurements

• Conclusions

TDCR technique in Radionuclide Metrology at ENEA

• TDCR technique was introduced at ENEA-INMRI in February 2011 by the

Hidex 300 SL TDCR counter “Metro” version and used for the first time in

the standardisation of a 63Ni source in the framework of the ESIR

comparison organised under the auspices of the BIPM

• An ENEA portable TDCR system working with the new front-end

electronics based on the Digital Pulse Processing (DPP) implemented in a

Fast Programmable Gate Array (FPGA) device was built in the framework of

the EMRP ENG08 Metrofission project

Metrofission: WP6&WP7 @ ENEA

WP6 & WP7 task:

Portable TDCR-LSC for in-situ

measurements

Development of the analysis and simulation SW based on CERN ROOT + GEANT4

Digitizer CAEN DT5720/B

Experimental Test

Research of components and

Materials (PMTs, optical chamber, etc)

Measurements between different LSC counters of a same radioactive solution and comparison with the results of the portable TDCR

• Portability • Fast Front End Electronics • Efficient and sensitive PMTs • Compact counter and user interface

PMTs for the ENEA portable TDCR

Quantum Efficiency (350 nm) 43%

Dynods MC/10

HV 900 V

Gain 1∙106

Transit Time 9,6 ns

• HAMAMATSU R7600U Series

• High quantum efficiency • Relative low voltage 900 V • Cathode to the Background for Photon Counting mode • 8th dynode output for spectroscopy

• Small dimensions (30x30mm) • Bialkali photocathode • Spectral range (300 ÷ 600 nm)

ENEA Portable TDCR system

• Optical chamber made in PTFE with prismatic shape

• Lift for the LS vial and optical shutter (PMT’s always powered)

• Compact design (HV modules included in the box)

• The C4900-50 PMT HV power supply units are on-board type with a design that aims at providing compactness, high performance and low power consumption. • The three HV power supply units are powered by a 12 V battery. • Maximum output voltage is +1250 V and can be regulated by a potentiometer • Dimensions of a single unit: 46x24x12 mm3 – Weight: 31g.

12 V battery

HV Power Supply

Electronics: Digital Approach

• Digital approach based on CAEN Desktop Digitizer DT5720/B – 4 acquisition channels

• Dimensions: 154 x 50 x 164 mm3 (W x H x D) • Weight: 680 g • A/D: 12 bits 250 MS/s ADCs • DPP: FPGA based for digital Charge

Integration/PSD Upgradeable via USB Link • INTERF: Control Software for Windows and

Linux • Readout USB (30 MB/s) • Electrical Power: 12 +/- 10% Vdc

http://www.caen.it

Electronics: DPP Firmware

Charge Integration (CI) (DT5720)

Trigger Time Tag ( 4 Byte ; 4 ns res.)

Charge ( 2 Byte) List Mode File TTT Charge

The Single Electron Peak

channels

ns

Histogram mode

a.u.

Waveform in oscilloscope mode

CAEN DAQ SW

• The DAQ SW developed by CAEN (g.mini@caen.it) after preliminary contact with ENEA to use the Digitizer with TDCR • It has been written following the main idea of the paper Bouchard J., Cassette P. ARI 52 (2000)

• The DAQ SW looks for coincidences comparing the TTTs and makes, like a black-box, the TDCR analysis

ENEA TDCR Analysis in ROOT

• By following the same MAC3 philosophy a script in C++ was developed at ENEA to analyze in the CERN ROOT framework (http://root.cern.ch/) the data recorded by the Desktop CAEN digitizer DT5720

• The script makes the TDCR analysis, saves the results in an ASCII file and produces a root tree

Energy spectrum

• The tree contains the data recorded events by events

Raw data (TTT and Charge)

Energy spectrum of Triple Coincidences

Asymmetry between the 3 channels for coincident events ea0t=(en0t-en1t); ea1t=(en0t-en2t); ea2t=(en1t-en2t);

channels

Time Interval Distribution

Original events (non dead time imposed) Events with a dead time imposed of 50 ms

ms

ms

By two other trees produced by the same script there is the possibility to plot the time interval distribution for all the 3 TDCR channels

63Ni measurements

• Dead Time imposed on the data of portable TDCR: 50 ms • Coincidence resolving window = 40 ns • TDCR parameters: ≈ 0.62 (portable TDCR) ; ≈ 0.80 (Hidex) • Data analyzed by TDCR07c.for code provide by CEA-LNHB (P. Cassette)

• Source prepared in glass vial filled with UG (10 mL) in our Radiochemistry Lab (Maria Letizia Cozzella) • 6 sources with mass of about 10 mg and different aliquot of CCl4 quenching agent for C-N • g-purity check of the master solution performed by HpGE detector (Aldo Fazio) • only sources without any quench used for TDCR measurements

Hidex

portable TDCR

C-N

30.00

30.10

30.20

30.30

30.40

30.50

30.60

30.70

30.80

30.90

31.00

0 0.5 1 1.5 2 2.5 3 3.5 4 Method

kB = 0.011 cm MeV-1

99Tc measurements

performed within an international comparison organised under the auspices of BIPM

• Source prepared in glass vial filled with UG (10 mL) in our Radiochemistry Lab (Maria Letizia Cozzella) • 12 sources with mass raging between 10 and 80 mg; CCl4 added in different aliquot as quenching agent for C-N measurements • g-purity check of the master solution performed by HpGE detector (Aldo Fazio) • only sources without any quench used for TDCR measurements

Hidex

portable TDCR

C-N

56.00

56.20

56.40

56.60

56.80

57.00

57.20

0 0.5 1 1.5 2 2.5 3 3.5 4

kB = 0.011 cm MeV-1

• Dead Time imposed on the data of portable TDCR: 50 ms • Coincidence resolving window = 40 ns • TDCR parameters: = 0.9419 (portable TDCR) = 0.9709 (Hidex) • Data analyzed by TDCR07c.for code provided by CEA-LNHB (P. Cassette)

99Tc Budget of uncertainties for portable TDCR

Quantity %

Counting statistics 0,250

Weighing 0,05

background 0,004

Dead time 0,1

Decay data 0.05

Half-life 0,01

Impurities 0,07

Absorption 0,02

TDCR value 0,02

PMT asymmetry 0,2

Ionization quench 0,2

Scintillator stability 0,1

Resolving time 0,1

Combined standard uncertainty 0.43

Comparison between the results obtained by the two SW codes (CAEN DAQ & ENEA ROOT)

Nuclide D %

63Ni 0,06 99Tc -0,37

D (%)=100*(1-a_ENEA/a_CAEN)

It is important to check the new digitizer technology with the MAC3 in reference conditions

Discussion and Perspectives

• A mini-TDCR prototype for measurements in-situ was built at ENEA-INMRI in the framework of the EMRP JRP Metrofission • 63Ni and 99Tc measurements were carried out by this prototype and compared with other LSC counters available at ENEA-IMRI based both on the 2PMTs technique and the TDCR technique (Hidex system “Metro” version)

• Two SW codes (CAEN DAQ and ENEA ROOT) for TDCR analysis of the data recorded by a CAEN Digitizer DT5720 are available at ENEA-INMRI

• New investigation on 3H and other nuclides (14C, 90Y, ..) are still in progress - a simulator based on GEANT4 is also in construction • Pulse shape discrimination and g-channel can be included thanks to the digitizer technology

Acknowledgments

• We’re very grateful to Mr Massimo Pagliari (ENEA-INMRI) and Mr Sergio Mancini (ENEA) for their mechanical and electronics competences and for the assistance given during this work • Thanks to Stefano Loreti (ENEA-INMRI) for some useful discussions on the CAEN digitizer • Many students (Eng Dr Carmine Biondi, Dr Valerio Di Sabatino from University “La Sapienza” – Rome , Mr Paulius Butkus from Vilnius University) who collaborated and are collaborating directly with me in this adventure …..

… Thank very much to all of you for your attention