A digital Compton suppression spectroscopy withoutgamma-ray coincidence-summing loss using list-modemultispectral data acquisition

Weihua Zhang • Pawel Mekarski • Maxime Dion •

Jing Yi • Kurt Ungar

Received: 8 December 2011 / Published online: 27 December 2011

� Akademiai Kiado, Budapest, Hungary 2011

Abstract The study demonstrates the advantages of an

innovative list-mode multispectral data acquisition system

that allows simultaneous creation of several different sin-

gle, summed, coincident and anticoincident spectra with a

single measurement. One of the consequences of list-mode

data file offline processing is a reconstructed spectrum with

Compton continuum suppression and without any full-

energy peak efficiency deduction owing to true coincidence

summing. The spectrometer is designed to read out ana-

logue signal from preamplifier of gamma-ray detectors and

to digitalize it using DGF/Pixie-4 software and card

package (XIA LLC). This is realized by converting an

Ortec Compton suppression data acquisition system into an

all-digital spectrometer. Instead of using its timing elec-

tronic chain to determine the coincidence event, the analog

signals from primary and guard detectors were connected

directly into the Pixie-4 card for pulse height and time

coincident measurement by individually logging and time

stamping each electronic pulse. The data acquired in list-

mode included coincidence and anticoincidence events

consisting of records of energy and timestamp from pri-

mary and guard detectors. Every event was stored in a text

file for offline processing and spectral reconstruction. A

sophisticated computer simulation was also created with

the goals of obtaining a better understanding of the

experimental results and calculating efficiency.

Keywords Digital gamma–gamma coincidence/

anticoincidence counting � List-mode data acquisition �Compton suppressions

Introduction

The Compton continuum suppression technique has been

used for several decades in the areas of neutron activation

analysis (NAA) [1–5], low-level radioactive waste and

environmental naturally occurring radioactivity measure-

ments [6–8]. One of the most important advantages of

Compton suppression gamma-ray spectrometry is the

substantial decrease of background activity, leading to

improved detection limits. However, its applications are

limited to certain types of disintegration schemes of the

nuclide used in the analysis. For examples, W. Zhang and

A. Chatt have judiciously applied the Compton suppression

NAA methods for a few trace element analyses such as,

iodine using 128I 442.9 keV gamma-ray, vanadium using52V 1,434.2 keV gamma-ray, copper using 66Cu

1,039.2 keV gamma-ray and arsenic using 76As 559.1 keV

gamma-ray with significant background suppression and

negligible full-energy peak deduction [9–12].

The limitations of the spectroscopic performance can be

ascribed to the basic principles of how a Compton sup-

pression spectrometer works. The Compton continuum is

caused by scattered photons escaping from the principal

detector. Each count in the Compton continuum is

accompanied by an escaping gamma-ray which can be used

to differentiate this count from photoelectric events by

employing anticoincidence and coincidence techniques.

The result is the suppression of the Compton continuum in

the gamma-ray spectrum. The most common method of

Compton continuum suppression involves the use of an

annular detector surrounding the principal detector crystal.

Compton scattering in the principal detector may produce

scattered gamma-rays that interact with the surrounding

annulus. If the two detectors are operated in anticoinci-

dence mode, most of the Compton interactions in the

W. Zhang (&) � P. Mekarski � M. Dion � J. Yi � K. Ungar

Radiation Protection Bureau, Health Canada,

775 Brookfield Road, Ottawa, ON K1A 1C1, Canada

e-mail: weihua.zhang@hc-sc.gc.ca

123

J Radioanal Nucl Chem (2012) 292:1265–1272

DOI 10.1007/s10967-011-1588-7

principal detector can be rejected. The photoelectric events

do not involve the escape of scattered radiation and thus are

not affected by the use of anticoincidence counting. One

disadvantage of this approach is also apparent. Nuclides

with complex decay schemes may emit many gamma rays

in coincidence. There is a possibility of two gamma-rays

from the same disintegration being detected by both

detectors at the same time. These events will be considered

as Compton events and rejected, leading to the undesired

full-energy peak efficiency deductions.

In order to solve this problem, a coincidence counting

technique has been developed. The same equipment as that

for the anticoincidence system is used except that it is in

the ‘‘coincidence mode’’ and ‘‘an energy window setting’’

of the surrounding detector is set up. When a specified

energy is deposited in the surrounding detector, it triggers

an output timing signal. The principal detector events

which are in coincidence with such a signal, and hence a

selected energy event in surrounding detector, will be

recorded in the spectrum. The idea is that one of the cas-

cading gamma-rays is used to gate the analog-to-digital

converter (ADC) so that another peak in the spectrum is

recorded with very low background. This technique is quite

suitable for cases of coincident gamma-ray emitting nuc-

lides because this additional energy requirement maintains

high full-energy peak efficiency while at the same time

reduces the Compton background. The major disadvantage

of this technique, however, is its special energy window

setting which explains why this technique cannot be used

for the multi-nuclides measurement. Even though extre-

mely low background can be obtained using the coinci-

dence counting technique, the problem of full-energy peak

deduction still cannot be solved as the cascaded gamma-

rays cannot be detected with a coincidence efficiency of

100%.

For low level radionuclide environmental monitoring

applications, an Ortec Compton suppression system [13]

was purchased and installed in our laboratory a few years

ago. The major difference between the system and other

conventional HPGe spectrometers was that it had two sets

of electronics. One set was sensitive to the timing rela-

tionship between signals from the principal and guard

detectors. Each timing electronic chain consisted of a

timing filter amplifier (TFA) and a constant fraction dis-

criminator (CFD). The signals from principal and guard

detectors were fed to separate TFAs. The negative analog

outputs from each TFA were then changed into timing

logic pulses in the CFD. The time logic pulses provided by

the primary detector and the guard detector were then

supplied to the start and stop inputs of a time to amplitude

converter/single channel analyzer (TAC/SCA), respec-

tively. The combined function of the TAC/SCA is to

determine coincidence events and generate gating pulse.

Whenever a coincidence event is detected, the energy

signal from the principal detector will be gated off, causing

the Compton continuum to be suppressed. The system can

also operate in conventional and coincidence counting

modes, but these methods have to run at different time with

a corresponding spectrum.

To be able to do simultaneous anticoincidence and

coincidence counting, the system has been converted into a

digital spectrometer in the study. Instead of using timing

electronic chain to determine the coincidence event, the

analog signals from primary and guard detectors were

connected directly into a Pixie-4 card (XIA LLC) for pulse

height and time coincident measurement. The data

acquired in list-mode (or time stamped) include coinci-

dence events consisting of records of energy and timestamp

from primary and guard detectors. Every single event is

processed and stored in a list-mode format text file for

offline analysis. The simplicity of the present coincidence

system is especially apparent in contrast to the system

associated with many NIM-based analog processing mod-

ules. The advantages of list-mode data acquisition include

individually logging and time stamping each electronic

pulse arising for each gamma-ray or X-ray interacting with

the spectrometer, which allows the simultaneous creation

of several different single, summed, coincident and anti-

coincident spectra from a single measurement. One of the

consequences of list-mode data file offline processing is a

reconstructed spectrum with Compton suppression and

without any full-energy gamma-ray peak efficiency loss.

Experimental

System description and calibration

The primary detector used in this study was an Ortec n-type

GMX HPGe coaxial detector with a crystal diameter of

66.2 mm and a length of 69.0 mm. This detector had a

peak-to-Compton ratio of 60:1 for the 1,332.5 keV peak of60Co, a relative efficiency of 25% with respect to a standard

NaI(Tl) detector at 1,332.5 keV of 60Co, and a resolution

(FWHM) of 0.85 keV at 122.1 keV peak of 57Co. The

HPGe detector endcap was made entirely of carbon fibre to

meet the high radiation transmission requirement. The

guard detector used in the system consisted of a 900 9 900

NaI(Tl) annulus with four photomultiplier tubes (PMTs)

and a 300 9 300 NaI(Tl) plug with one PMT. The peak-to-

Compton plateau ratio of this system was 1,065:1 at the

661.7 keV peak of 137Cs, using the IEEE convention of the

number of counts per channel in the Compton plateau

(358–382 keV). The geometric arrangement of primary

and guard detectors is shown in Fig. 1. As shown in the

figure, the primary HPGe detector was inserted into one

1266 W. Zhang et al.

123

end of the NaI(Tl) annular guard detector; and a NaI(Tl)

plug was placed at the other end to maximally detect

photons escaped from the HPGe. Two separate high volt-

age (HV) power supplies (Ortec model 556) were used for

the NaI(Tl) detectors. One of them was connected to the

PMT of the plug detector. Each of the four PMT on the

annulus was connected through a junction box to the other

HV power supply. The outputs from all four PMTs were

collected using T-connection into one cable which was

used for annulus detector waveform signal output.

The data-acquisition system for the spectrometer utilizes

all-digital electronics based on the XIA LLC Digital

Gamma Finder (DGF)/Pixie-4 software and card package

[14]. The Pixie-4 card is a four channel digital pulse-pro-

cessing module. As shown in Fig. 1, the waveform signals

from preamplifier of HPGe, PMTs of NaI(Tl) annulus and

PMT of NaI(Tl) plug detectors were fed into three different

channels of the Pixie-4 card for pulse height and time

coincident measurement. At each channel, the input signals

were continuously sampled and digitized by a 14-bit ADC.

The signal pulse height was determined to 16-bit resolution

by a programmable digital trapezoidal energy filter

implemented in a field-programmable gate array (FPGA).

Event timing and pulse-pileup inspection was also carried

out in the FPGA by a fast programmable trapezoidal trigger

filter. Events were time-stamped at the full ADC rate of

75 MHz. The coincidence time window was also set in the

software with a step of 13.33 ns and a lower limit of

79.33 ns, thus allowing accurate reconstruction of coinci-

dent interactions. Table 1 gives a list of all the coincident

and anticoincident events that were stored in the list-mode

data file.

The Pixie-4 card is deployed on a chassis with Compact

PCI/PXI backplane from National Instruments. A host desktop

PC controls the pulse processing module and performs data

readout. All operating parameters, including the filter values,

are user adjustable in the software on the host PC. The

parameters of trapezoidal trigger and energy filter, such as

trigger threshold, filter rise and flat top time, are optimized by

maximizing the output and input count rate ratio and mini-

mizing the 661.7 keV peak resolution of 137Cs. Whenever a

valid event is detected, a digital signal processor (DSP) reads

out the energy filter values, reconstructs the pulse height, and

bins the energy. In the case of coincidence counting, the DSP

obtains the coincidence pattern of active channels in a given

event. Three certified standard point sources (137Cs, 22Na and60Co) from Eckert and Ziegler Analytics were used for the

energy, resolution and full-energy peak efficiency calibrations

of each detector. By tuning each PMT’s high-voltage supply,

and gain, and offset of each Pixie-4 card input channel, the

same full-energy gamma-ray appears in almost the same center

channel for both NaI(Tl) and HPGe detectors.

System modeling

The system modeling was conducted using the Geant4

Toolkit [15]. All of the data processing and output was

performed through the implementation of abstract inter-

faces for data analysis (AIDA) [16]. The HPGe detector

consisted of a cylinder with a diameter of 66.2 mm and a

height of 69.0 mm, which was placed within a 0.76 mm

thick carbon end cap with an inner diameter of 75.8 mm.

The radioactive source was defined to be either a point

source or a small cylindrical source, either of which were

Fig. 1 Schematic drawing of

the detector arrangement and

Pixie-4 digital multispectral

acquisition spectrometer

Table 1 Allowed coincidence hit patterns by Pixie-4 card

Event descriptions NaI(Tl) plug,

channel-1

HPGe,

channel-2

NaI(Tl) annulus,

channel-3

1. Coincidence between HPGe and NaI(Tl) plug 1 1 0

2. Coincidence between HPGe and NaI(Tl) annulus 0 1 1

3. Triple coincidence in HPGe and NaI(Tl) plug and annulus 1 1 1

4. Anticoincidence between HPGe and NaI(Tl) plug and annulus 0 1 0

Digital Compton suppression spectroscopy 1267

123

placed directly on top of the carbon end cap. The NaI(Tl)

annulus had an inner diameter of 91.0 mm and an outer

diameter of 229.0 mm, which was surrounded by alumi-

num shielding of varying thickness. The plug detector was

a solid cylinder of NaI(Tl) that was placed above the ger-

manium detector, in the central hole of the annulus. The

distance of the plug could be changed depending on the

simulation to move the plug closer or farther away from

the end cap and radioactive source. The diameter of the

NaI(Tl) in the plug was 76.2 mm and it was also sur-

rounded by 3.15 mm thick aluminum shielding.

The standard electromagnetic (EM) package was used in

this simulation. It contained the following processes:

photo-electric effect, Compton scattering, pair production,

bremsstrahlung, ionization, multiple scattering, and anni-

hilation. Its effective energy range begins from 100 eV and

0.5

5

50

500

5000

50000

(a)

(b)

0 500 1000 1500 2000

Cou

nts

Energy, keV

HPGe normal spectrum

HPGe-plug coincidence

HPGe-annulus coincidence

HPGe-plug-annulus triple coincidence

HPGe anticoincidence with plug and annulus

0.5

5

50

500

5000

50000

0 500 1000 1500 2000

Cou

nts

Energy, keV

HPGe normal spectrum

HPGe-plug coincidence

HPGe-annulus coincidence

HPGe-plug-annulus triple coincidence

HPGe anticoincidence with plug and annulus

Fig. 2 a List-mode data offline

processed normal, coincidence

and anticoincidence HPGe

gamma-ray spectra of 22Na from

one measurement;

b computational modelling

calculated spectra using Geant4

1268 W. Zhang et al.

123

extends up to the TeV energy range. Along with the EM

package the standard decay and radioactive decay physics

processes were also included.

Results and discussion

The 22Na standard point source was measured by the sys-

tem. The list-mode data were collected by the measurement

over 120 s at a 92.66 ns coincidence window. As listed in

Table 1, the data acquired in list-mode included coinci-

dence and anticoincidence events consisting of records of

energy in DSP units and timestamp from HPGe, NaI(Tl)

plug and NaI(Tl) annulus detectors. The list-mode data

collected on an event-by-event basis, which is like

‘‘solidified electronic pulses’’, were stored in a text file for

offline analysis. During offline analysis, the events (or solid

electronic pulses) were initially grouped into different

coincidence and anticoincidence counting mode arrays.

The DSP units for each coincidence and anticoincidence

events in these arrays were divided by detector’s [HPGe or

NaI(Tl)] energy calibration factor, then histogrammed to

gamma–gamma coincident or anticoincident energy spec-

trum, correspondingly. The one-dimensional histogrammed

HPGe spectra in different counting mode obtained by

offline list-mode data process are illustrated in Fig. 2a.

Compared with the HPGe normal spectrum, as shown in

Fig. 2a, the Compton continuum has been extensively

suppressed in the anticoincidence spectrum. However as a

result of the annihilation process, the 511.0 keV peak areas

were significantly reduced by 97%, as listed in Table 2.

The 1,274.5 keV peak areas were also reduced by 86%

compared to HPGe normal spectrum, which is slightly less

than that of 511.0 keV peak. The reason is that there is

about 10% of all the 1,274.5 keV gamma-ray emitted from22Na proceed by electron capture instead of positron decay.

It should also be noted in Table 2 that the rejected 511.0

and 1,274.5 keV counts in anticoincidence counting have

mostly been recorded by other coincidence counting

modes. In the same measurement, the rejected 511.0 keV

gamma-rays in anticoincidence counting have been mostly

registered by the triple coincidence (56%) secondly by the

HPGe and NaI(Tl) plug coincidence (32%); HPGe and

NaI(Tl) annulus coincidence only registered 8%. The

rejected 1,274.5 keV counts in anticoincidence counting

have also been mostly recorded by the triple coincidence

(44%). The HPGe and annulus coincidence counting is

about 37%; while the HPGe and plug coincidence counting

only registered 6%, which shows a different pattern from

that observed with 511.0 keV peak. This is due to the fact

that the two 511.0 keV annihilation gamma-rays emit

always with an angle of 180� between each other.

The 60Co standard source was also measured by the

system. Using the same procedure, the spectra in different

counting mode obtained by offline list-mode data process

were illustrated in Fig. 3a. The 60Co decays primarily by

the emission of two coincident gamma-rays with a mean

life time of 8 9 10-13 s for the 1,332.5 keV gamma-ray

excited state. This time is so short that the events detected

by the HPGe detector and the NaI(Tl) annulus or plug

detector will be seen as taking place at the same time and

be rejected as a Compton event. As shown in Fig. 3a, in the

anticoincidence spectrum, the peak areas of 1,173.2 and

1,332.5 keV gamma-rays are reduced both by 70% com-

pared to the normal HPGe spectrum. As listed in Table 2,

the rejected counts in anticoincidence counting have been

registered mostly by the HPGe and annulus coincidence

counting (about 47% for both), then followed by HPGe and

plug coincidence counting (about 16% for both), and the

triple coincidence (about 8% for both). The coincidence

recovery rates of the two gamma-ray peaks show the same

behaviours.

A computer program was made that could specifically

search all the 511.0 and 1,274.5 keV peaks in different

coincidence counting spectra and select relevant evens or

solid pulses in these coincidence counting mode arrays

created by offline list-mode data processing in the 22Na

measurement. These selected events were then added to the

Table 2 The peak areas in different counting mode from the 22Na and 60Co measurement as shown in Figs. 2a and 3a

Gamma-ray energy (keV) The counts of peak area

Coincidence Anticoincidence

HPGe-plug, HPGe-annulus, triple No-constructed, constructed

By the 22Na measurement

511.0 121,962 (0.32), 24,985 (0.08), 201,126 (0.56) 14,788 (0.03), 354,664 (0.97)

1,274.5 5,032 (0.06), 24,313 (0.37), 35,650 (0.44) 11,019 (0.14), 73,393 (0.97)

By the 60Co measurement

1,173.2 16,872 (0.15), 33,936 (0.47), 8,298 (0.09) 41,866 (0.30), 92,977 (0.99)

1,332.5 15,322 (0.16), 27,973 (0.47), 5,811 (0.08) 34,705 (0.29), 82,300 (0.99)

The full-energy peak efficiency deduction factors (i.e. the ratios of corresponding peak area to normal spectrum) are listed in bracket

Digital Compton suppression spectroscopy 1269

123

anticoincidence counting mode array before it was histo-

grammed to get the reconstructed anticoincidence spec-

trum, which was as shown in Fig. 4a. As listed in Table 2,

the full-energy peak deduction factors of 511.0 and

1,274.5 keV gamma-ray peaks in the reconstructed 22Na

anticoincidence spectrum have been increased from 0.03 to

0.97 and from 0.14 to 0.97 respectively. Using the same

program, the anticoincidence spectrum of 60Co has been

reconstructed and shown in Fig. 4b. Compared to its no-

reconstructed anticoincidence spectrum, the full-energy

0.5

5

50

500

5000

(a)

(b)

0 500 1000 1500 2000 2500

Cou

nts

Energy, keV

HPGe normal spectrum

HPGe-plug coincidence

HPGe-annulus coincidence

HPGe-plug-annulus triple coincidence

HPGe anticoincidence with plug and annulus

0.5

5

50

500

5000

50000

0 500 1000 1500 2000 2500

Cou

nts

Energy, keV

HPGe normal spectrum

HPGe-plug coincidence

HPGe-annulus coincidence

HPGe-plug-annulus triple coincidence

HPGe anticidence with plug and annulus

Fig. 3 a List-mode data offline

processed normal, coincidence

and anticoincidence HPGe

gamma-ray spectra of 60Co from

one measurement;

b computational modelling

calculated spectra using Geant4

1270 W. Zhang et al.

123

peak efficiency deduction factors of 1,173.2 and 1,332.5 keV

gamma-rays were increased from about 0.30 to 0.99. The

background resulting from Compton scatters in both

reconstructed anticoincidence spectra could still be kept

low as before.

The multiple spectra of 22Na and 60Co in Figs. 2b and

3b were obtained by Geant4 simulations. The comparison

of simulated and experiment spectra in Figs. 2 and 3 show

an overall agreement between the measurement and sim-

ulation, except the presence of the apparent Compton

continuum discrepancy in the different counting modes.

Generally, the simulation gives lower Compton continuum

than those obtained by measurement with the exceptions

of HPGe-plug coincidence of 22Na measurement and

0.5

5

50

500

5000

50000

(a)

(b)

0 500 1000 1500 2000

Cou

nts

Energy, keV

HPGe normal spectrum

Reconstructed HPGe anticoincidence with plug and annulus

0.5

5

50

500

5000

0 500 1000 1500 2000 2500

Cou

nts

Energy, keV

HPGe normal spectrum

Reconstructed HPGe anticoincidence with plug and annulus

Fig. 4 Comparison of the

HPGe normal gamma-ray

spectrum and reconstructed

anticoincidence spectrum from

the same measurement by 22Na

(a) and 60Co (b)

Digital Compton suppression spectroscopy 1271

123

HPGe-annulus coincidence of 60Co measurement. The

discrepancy may be possibly attributed to the contributions

of shielding materials that is not included in the Geant4

simulation code and to the lack of precise dimension of the

crystal and its position in the detector housing. Even if the

differences between the simulated and measured responses

are mainly caused by inaccuracies in the modeling of the

physical geometry and material behaviour, the gaps can be

made smaller by properly optimizing the integrated para-

metric timing of the trapezoidal trigger and energy filters,

as well as pulse fitting. The events in the simulation do not

involve any electronic timing parameters. It always gives

the best case scenarios in the timing. Comparing simulated

Compton continuum with experimental results may be a

good way of shedding light on many distinctive features of

experiment spectra and could be used to predict and opti-

mize the performance of the system to get the best coin-

cidence/anticoincidence counting.

Conclusions and future work

In this study, an Ortec Compton suppression system has

been converted into a digital spectrometer that is able to do

simultaneous gamma–gamma anticoincidence and coinci-

dence multispectral counting with list-mode data acquisi-

tion. It has been demonstrated that the reconstructed HPGe

anticoincidence spectra by 22Na and 60Co point sources

have significant Compton background suppression without

any gamma-ray coincidence-summing losses at their full-

energy photon peaks. The gamma–gamma coincident event

distributions in different parts of the NaI(Tl) guard detector

with HPGe primary detector for 511.0, 1,274.5, 1,173.2

and 1,332.5 keV photons are also studied. It has been

shown that a significant coincidence pattern in various

parts of guard detector exists due to gamma–gamma

directional correlation by different radioactive decay

modes. Future development of the spectroscopy includes

the integrated parametric timing optimization and a com-

parative study of analog and digital detector systems to

increase the peak to Compton ratio of the newly developed

digital system. A computer program is also under devel-

opment for processing complex spectra containing several

unknown nuclides.

References

1. Kapsimalisa R, Landsbergera S, Ahmedb YA (2009) The deter-

mination of uranium in food samples by Compton suppression

epithermal neutron activation analysis. Appl Radiat Isot 67(12):

2097–2099

2. Landsberger S, Kapsimalis R (2009) An evaluation of Compton

suppression neutron activation analysis for determination of trace

elements in some geological samples. Appl Radiat Isot 67(12):

2104–2109

3. Nyarko BJB, Akaho EHK, Fletcher JJ, Chatt A (2008) Neutron

activation analysis for Dy, Hf, Rb, Sc, Se in some Ghanaian

cereals, vegetables using short-lived nuclides, Compton sup-

pression spectrometry. Appl Radiat Isot 66(8):1067–1072

4. Nicholson G, Landsberger S, Welch L, Gritzo R (2008) Char-

acterization of a Compton suppression system, the applicability

of Poisson statistics. J Radioanal Nucl Chem 276(3):577–581

5. Stover T, Lamaze G (2005) Compton suppression for neutron

activation analysis applications at the national institute of stan-

dards, technology (NIST). Nucl Instrum Methods Phys Res Sect

B: Beam Interact Mater Atoms 241(1–4):223–227

6. Nyarko BJB, Bredwa-Mensah Y, Serfor-Armah Y, Dampare SB,

Akaho EHK, Osae S, Perbi A, Chatt A (2007) Investigation of

trace elements in ancient pottery from Jenini, Brong Ahafo

region, Ghana by INAA and Compton suppression spectrometry.

Nucl Instrum Methods Phys Res Sect B: Beam Interact Mater

Atoms 263(1):196–203

7. Bacchi MA, Santos LGC, De Nadai Fernandes EA, Bode P,

Tagliaferro FS, Franca EJ (2007) INAA with Compton suppres-

sion: how much can the analysis of plant materials be improved?

J Radioanal Nucl Chem 271(2):345–351

8. Nyarko BJB, Akaho EHK, Fletcher JJ, Zwicker B, Chatt A

(2006) Simultaneous determination of short-to-medium lived

nuclides in Ghanaian food items using INAA, Compton sup-

pression counting. J Radioanal Nucl Chem 270(1):243–248

9. Zhang W, Chatt A (1998) Compton suppression spectrometry

coupled to instrumental neutron activation for iodine in biological

materials. Trans Am Nucl Soc 78:95–96

10. Zhang W, Chatt A (2000) Determination of vanadium by

instrumental neutron activation analysis in conjunction with

Compton suppression gamma-ray spectrometry. Trans Am Nucl

Soc 83:486–488

11. Zhang W, Chatt A (2000) Determination of copper by neutron

activation analysis in conjunction with Compton suppression

gamma spectrometry. Trans Am Nucl Soc 82:92–93

12. Zhang W, Chatt A (1997) Compton suppression spectrometry for

arsenic in biological reference materials. Trans Am Nucl Soc

77:11–12

13. Paulus TJ, Keyser RM (1991) Compton suppression systems for

environmental measurements. In: International conference on

methods and applied radioanalytical chemistry (MARC-II), Kona

14. Hennig W, Chua YX, Tana H, Fallu-Labruyerea A, Warburtona

WK, Grzywaczb R (2007) The DGF Pixie-4 spectrometer:

compact digital readout electronics for HPGe clover detectors.

Nucl Instrum Methods Phys Res Sect B Inter Mater Atoms

263(1):175–178

15. Geant4 Collaboration, Agostinelli S et al (2003) Accelerators,

spectrometers, detectors and associated equipment. Nucl Instrum

Methods Phys Res A 506(3):250–303

16. Vincenzo I, Lorenzo M, Andreas P (2003) Review of the abstract

interfaces for data analysis (AIDA) from a developer’s perspec-

tive. CERN version1.0

1272 W. Zhang et al.

123