A prototype of a portable TDCR system at ENEA.

Applied Radiation and Isotopes ∎ (∎∎∎∎) ∎∎∎–∎∎∎

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A prototype of a portable TDCR system at ENEA Marco Capogni n, Pierino De Felice ENEA, Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti (INMRI), C.R. Casaccia, Via Anguillarese, 301, I-00123 Rome, Italy

H I G H L I G H T S

New miniaturized TDCR device at ENEA-INMRI. Digital approach to the TDCR coincidence acquisition and analysis. 63 Ni and 99Tc activity measurements. CAEN and ENEA off-line coincidence analysis software for TDCR measurements. TDCR first implementation of α/β pulse shape discrimination.

art ic l e i nf o

a b s t r a c t

Keywords: Portable TDCR Digitizer Pure β-emitting radionuclides Pulse shape discrimination

A prototype of a portable liquid scintillation counting system based on the Triple-to-Double Coincidence Ratio (TDCR) technique was developed at ENEA-INMRI in the framework of the European Metrofission project. The new device equipped with the CAEN digitizers was tested for the activity measurements of pure β-emitters (99Tc and 63Ni). The list-mode data recorded by the digitizers were analyzed by software implemented in the CERN ROOT environment, which allows the application of pulse shape discrimination using the new device. & 2014 Elsevier Ltd. All rights reserved.

1. Introduction A new miniaturized TDCR system was developed at ENEA-INMRI in the frame of the project “Metrology for new generation nuclear power plants” (Johansson et al., 2011), also known as the Metrofission project, jointly funded by the European Metrology Research Programme (EMRP). In particular the realization of a portable self-calibrated TDCR counter equipped with front-end electronics making use of the new digital pulse processing (DPP) technology was the main technical and scientific task of the Work Packages 6 and 7 of the EMRP ENG08 Metrofission project. The TDCR method is a well established liquid scintillation counting (LSC) technique in radionuclide metrology (Broda et al., 1988, 2007); it is essentially based on Poisson statistics, in order to consider the light emitting processes in liquid scintillation due to the energy loss of a charged particle in it, and on the Birks’ function to take into account the ionization quenching phenomenon. The TDCR method is suitable for activity measurements of a number of radionuclides and does not need any reference source. TDCR counters comprise 3 photomultiplier tubes (PMTs) which, in most cases, are symmetrically arranged around the liquid scintillation vial to be

n

Corresponding author. Tel.: þ 39 06 3048 6628; fax: þ39 06 30484650. E-mail address: [email protected] (M. Capogni).

measured. An optical chamber with high reflectivity, and a specific electronic system for the treatment of the coincident pulses of any pair of PMTs (“double coincidences”, D) and all three PMTs (“triple coincidences”, T) are required to apply the TDCR method. However, most TDCR devices operating in the world are home-made counters developed at National Metrology Institutes (NMIs). Because of their large size and weight these instruments cannot be used for in-situ measurements, as required by many applications of radioactivity measurements in the field of nuclear energy, nuclear medicine, environment, etc. The ENEA-INMRI portable TDCR detection system was developed to meet the objectives of the Metrofission project without losing the main characteristics of a TDCR counter (Cassette and Bouchard, 2003). A dedicated study was performed to select electronic and optical components to ensure optimal performance of the new detection system. An intensive scientific collaboration was established with the Italian CAEN firm to implement and optimize a portable digital coincidence counting (DCC) system for TDCR data acquisition. Measurements of pure-beta-emitting radionuclides, 99Tc and 63Ni, were performed with the new TDCR counter by using radioactive solutions standardized in the framework of two international comparison exercises (CCRI(II)-K2.Tc-99 and the International Reference System extended to β emitters) organized during 2011 and 2012 under the auspices of the Bureau International des Poids et Mesures (BIPM) in Sèvres. In addition, the pulse shape discrimination

http://dx.doi.org/10.1016/j.apradiso.2014.03.021 0969-8043/& 2014 Elsevier Ltd. All rights reserved.

Please cite this article as: Capogni, M., De Felice, P., A prototype of a portable TDCR system at ENEA. Appl. Radiat. Isotopes (2014), http: //dx.doi.org/10.1016/j.apradiso.2014.03.021i

M. Capogni, P. De Felice / Applied Radiation and Isotopes ∎ (∎∎∎∎) ∎∎∎–∎∎∎

2

Fig. 1. (a) The new portable TDCR system. (b) The optical chamber: external view (up) and internal view (down). (c) The design of the optical shutter.

(PSD) technique for α/β separation was explored with the new portable system in the domain of the TDCR method. To this end, a liquid scintillation source containing a mixture of 90Sr and 241Am was measured.

and removed via a manual lift without the need to turn off the HV supply to the PMTs. Both lift and optical shutter were realized at ENEA-INMRI by using Teflons. The total weight of the new detector is less than 6 kg. A picture of the optical chamber is shown in Fig. 1b. A design of the optical shutter is shown in Fig. 1c.

2. The new portable TDCR detection system

2.2. The photomultiplier tubes

The aim of this work was to build a compact and portable TDCR device to meet the requirements of the Metrofission project (Cassette et al., 2013). Compactness and portability of the detection system were realized by using PTFE (Teflons) for the detector housing, for the optical chamber and for each housing of the square miniature PMTs. In addition, the PMTs outputs were linked directly to the inputs of the desktop-type CAEN digitizer belonging to the DT5720 family (CAEN, 2014). The new TDCR detection system is shown in Fig. 1a.

Three Hamamatsu R7600U-200 square metal package type photomultiplier tubes were selected for the new TDCR detector. The PMTs are characterized by small dimensions (30 mm 30 mm), relatively wide spectral response (300C600 nm), high-quantum efficiency, and relatively low supply voltage (approximately 900 V) with the cathode grounded to operate in the photon counting mode. The PMTs are powered by three compact (dimensions: 46 24 12 mm3, weight: 31 g), on-board type HV power supply units (C4900 series, provided by Hamamatsu Photonics). The HV power supply units have low power consumption and are supplied by a 12 V battery.

2.1. The optical chamber 2.3. The digitizer A first version of the new portable TDCR device is described by Capogni et al. (2013). The optical chamber of the new TDCR detector, entirely built at ENEA-INMRI, has an inner prismatic shape, with equilateral triangular base (L¼ 60 mm and H ¼73 mm), and an outer cylindrical shape. This particular shape was selected to fit the square geometry of the PMTs used and to allow the vials to be placed in close proximity of the three PMTs to maximize the geometric efficiency. The optical chamber is made from white Teflons and is enclosed in a black cylindrical box (ϕ ¼150 mm and H ¼150 mm), also made from Teflons, to fit precisely with this box. In the final version of the new TDCR detector presented in this paper the optical chamber is closed at the top by an optical shutter that allows the vials to be inserted

The new DPP front-end electronics used for nuclear measurements and based on the field-programmable gate array (FPGA) technology was introduced in many NMIs for coincidence measurements in the radioactivity field as it is the TDCR technique (Keightley and Park, 2007; Bobin et al., 2012). Recent advances in the use of the DPP technology in the radionuclide metrology techniques for primary standardization are described by Keightley et al. (2013). The use of the digitizer technology in TDCR measurements at ENEA-INMRI was described by Capogni and Antohe (2014) and Mini et al. (2014). To perform the work described in this paper, the new portable TDCR detector was equipped with both DT5720 and DT5720B desktop-type CAEN digitizers. Using



Acquisition window Long Gate Short Gate

Threshold

Baseline

3

completely covered in time by the gate pulse. A typical SEP spectrum recorded by the new TDCR counter equipped with the digitizer DT5720, with the PMTs biased around 900 V and without any vial inside the optical chamber, is shown by Mini et al. (2014). The digitizer was applied in the histogram mode to match the PMTs and have the same gain in the three different channels or, in other words, to have the 3 SEPs located at the same channel.

Trigger

3.2. The analysis software

Time

Time tag

Record length (in samples)

Fig. 2. Long Gate and Short Gate with the trigger configuration in the desktop-type CAEN digitizer DT5720B.

the terminology introduced by Mini et al. (2014), both devices are provided with fast and precise ADC (250 MegaSamples/s, 12 bit). For each triggered pulse and within a time acquisition window, the DT5720B version allows the setting of two different gate widths (“Long Gate” and “Short Gate”), related in time as shown in Fig. 2, for the ADC conversion of the input signal by running a DPP-PSD firmware. More specifically, the Long Gate covers in time the whole input pulse while the Short Gate overlaps with the maximum amplitude of this pulse. This feature is particularly interesting in applications of the PSD technique (L'Annunziata, 2012) which requires the discrimination of the slow and the fast components of the analog pulse coming from a liquid scintillation detector. In fact, by performing the above double gate integration over the input pulse it is possible to calculate the total charge (Qlong) and the partial charge (Qshort) of the signal inside the “Long Gate” and “Short Gate” window respectively. The data elaborated and recorded by the DT5720B module are saved in a file (ASCII or Binary format) as a stream of trigger time tag (TTT) and two charge values (Qshort and Qlong); this means that the size of a single event is very small (typically a few bytes). The stored list-mode data file can be shared between different users and analyzed independently with different codes.

The digitizers are dead-timeless acquisition devices and customized software written in C þ þ (Mini et al., 2014) was provided by CAEN to manage the dead-time and for the off-line coincidence analysis between the different signals coming from each PMT of a TDCR system by emulating the MAC3 logic (Bouchard and Cassette, 2000). Different software was developed at ENEA-INMRI (Butkus, 2013) for the off-line analysis of the TDCR events recorded by the CAEN digitizers. This software was implemented in CERN ROOT frame (Brun and Rademakers, 1997) following the same MAC3 philosophy (Capogni and Antohe, 2014). The ENEA-INMRI software reads the data recorded by the CAEN digitizer and organizes them, event by event, as “leaves” of a ROOT tree file; this also allows the visualization of the charge and time spectra of the recorded events for each PMT of the TDCR device. The algorithms implemented in this software to perform the off-line TDCR analysis also allow the determination of the exponential time-interval distribution, ti (μs), between successive nuclear disintegrations from the list-mode data file recorded for each PMT by imposing a defined dead-time, tdead (μs), and a fixed coincidence resolving time, tc (ns), window on the recorded events of the 3 PMTs. In Fig. 3 the exponential time-interval distribution calculated from the list-mode data file recorded by the DT5720 digitizer by imposing a tdead ¼50 μs is shown for a 99Tc source. In this figure the effects of the extendabletype tdead management of the recorded events are clearly visible (Müller, 1971). In addition to performing, for defined tdead and tc values, the off-line TCDR analysis, by computing the single counts of each PMT (A, B, and C), the sum (S) of them, the coincidence counts (AB, BC, AC, D and T), the real time (treal), the live time (tlive) and the TDCR parameter (TDCR ¼T/D), the ENEA-INMRI software also includes an algorithm to apply the PSD technique to the TDCR method. In fact, by using the DT5720B digitizer it is possible to read the (TTT, Qshort, Qlong) values for each event, to compute the parameter PSD ¼1 Qshort/Qlong and to add it as a “leaf” to the ROOT tree file mentioned above. So, for each event it is possible to

3. The TDCR setting and analysis software A crucial point of the TDCR method is the precise adjustment of the discrimination threshold below the single-electron peak (SEP) and above the noise for each one of the three PMTs (Cassette and Bouchard, 2003). A very accurate and fast logic device is also necessary to perform the management of dead-time (Bouchard, 2000) and the coincidence analysis between the signals generated by each PMT. 3.1. The single electron peak The correct setting of the working parameters of the new portable TDCR device was established by looking at the SEP generated by each PMT and recorded by the digitizer device. The discrimination threshold and the width (typically 24 ns) of the ADC gate were imposed by using the control software of the digitizer for each individual channel, in order to suppress the noise and to have the whole analog pulse coming from the PMT

Fig. 3. Time-interval distribution, ti (μs), on real events recorded by one PMT and obtained by applying the extendable-type dead-time.



4

represent the pair of values (PSD, Qlong) in a bi-dimensional plot, to apply a graphical cut in order to select in this plot a region of interest and to save the selected events in a file on which the offline TDCR analysis can be performed.

4.

63

Ni and

99

Tc activity measurements

The new portable TDCR detector equipped with both DT5720 and DT5720B digitizers was used to measure the activity concentration of a low-energy beta nuclide (63Ni) and, for the first time, a medium-energy beta nuclide (99Tc). No differences were found between the results obtained with the two digitizers for both radionuclides, provided that the same settings (discrimination threshold and gate width of 24 ns) used for the DT5720 version were applied to the DT5720B digitizer. For the latter, only the Qlong value recorded with a Long Gate¼ 24 ns was used to perform the TDCR analysis. This means that the algorithm used to integrate the charge of the analog signal is the same in the two version of firmware installed in the respective digitizers. The sources had been prepared by the radiochemistry laboratory of the ENEAINMRI for participation in two international comparisons organized by the CCRI(II) in 2011 and 2012 under the auspices of the BIPM. The 63Ni comparison was devoted to the extension of the International Reference System (SIR) to pure beta emitters (Ratel et al., 2013). A preliminary gamma-impurity check was performed on the two master solutions by high energy-resolution HPGe spectrometry. Two sets of 6 sources, one for each nuclide, were available for LSC measurements. The sources contained 10 mL of Ultima Gold (UG) as a liquid scintillator in high-performance 20 mL glass vials and approximately 10 mg of radioactive solution (with different aliquots of CCl4 as a quenching agent). One blank source was prepared for background measurements, containing only 10 mL of UG in the same geometry mentioned above. The sources were prepared following the same procedure described by Capogni et al. (2012) in order to be standardized by two primary techniques: the CIEMAT/NIST LSC efficiency tracing method (hereinafter called the CIEMAT/NIST method), using the Packard Tricarb3100TR counter (hereinafter called Tricarb counter), and the TDCR method, using the Hidex 300SL “Metro” version counter (hereinafter called the Hidex counter). 3H in aqueous solution was used as a tracer in the CIEMAT/NIST method; for the TDCR measurements only the source without any aliquot of CCl4 (hereinafter called the unquenched source) was used for each set. Typical background counting rates measured at ENEA-INMRI using the two TDCR systems are RT ¼10 s 1and RD ¼ 14 s 1 for the new portable TDCR counter and RT ¼0.7 s 1 and RD ¼ 1.25 s 1 for the Hidex counter, where RT ¼ T/tlive and RD ¼ D/tlive.

Fig. 4.

4.1.

63

Ni

The radionuclide 63Ni is of particular interest and importance in metrology and in TDCR measurements (Razdolescu et al., 2006; Collé et al., 2008; Wanke et al., 2012), due to its very long half-life and the very low energy of the beta particle emitted (Eβ,avg ¼17.434 (4) keV) (Bé et al., 2006), as well as for radiation protection surveillance around nuclear facilities. A measurements campaign of this nuclide was therefore carried out at ENEA-INMRI. The unquenched 63Ni source from the previously prepared set was repeatedly measured for a period of one month using the new portable TDCR device, by setting a counting time tcount ¼ 1200 s for each measurement. The data stream recorded was then analyzed both by the CAEN and the ENEA analysis software by applying a range of coincidence resolving time (varying between tc ¼ 20 and 500 ns) and for two values of dead-time (tdead ¼10 and 50 μs). For each set of analyzed data the ratios RT/RAB, RT/RBC and RT/RAC were computed from the net count rates of the triple coincidences, RT, and the net count rates of the double coincidences (RAB ¼AB/tlive, RBC ¼BC/tlive and RAC ¼AC/tlive) from the three pairs of PMTs, and used to calculate the efficiencies for the logical sum of the double coincidences (εD) and for the triple coincidences (εT) by using the code TDCR07c written in Fortran 77 and provided by LNHB-CEA. A TDCR parameter of 0.62 was obtained compared to 0.80 obtained from the same source using the Hidex counter. The activity concentration of the 63Ni solution was then computed from the net count rate of the triple coincidences, RT, of the logical sum of the double coincidences, RD, and the related efficiencies. In Fig. 4 the 63Ni activity concentration values determined by the portable TDCR system and analyzed by applying the ENEA code for different values of tc and for the two values of tdead are shown (Birks’ parameter kB¼0.011 cm MeV 1 ¼kB0). In Table 1 the 63Ni activity concentration (for kB¼kB0) measured using the new portable TDCR system for tc ¼140 ns is compared with results obtained from the same source using the Hidex counter and the CIEMAT/NIST method, by using the same Birks’ parameter value, kB0, and tc ¼40 ns for the Hidex counter and tc ¼18 ns for the Tricarb counter. 4.2.

99

Tc

99 Tc is an interesting radionuclide, both for radioprotection and metrology applications. The standardization of this nuclide requires special attention because of uncertainties related to the “shape factors” of the Fermi's beta-decay theory (Laureano-Perez et al., 2010; Zimmerman et al., 2010; Wanke et al., 2012; van Wyngaardt et al., 2014). With the CCRI(II)–K2.Tc-99 comparison the ENEAINMRI participated in a key comparison using the new portable TDCR system for the first time. Similarly to the 63Ni measurements,

Ni activity concentration as a function of different values of tc (kB ¼ 0.011 cm MeV 1).

63



two primary LSC techniques (CIEMAT/NIST and TDCR methods) were applied for the 99Tc standardization. For the CIEMAT/NIST method the set of 6 sources prepared as described above were measured, with 3H applied as the tracer. For TDCR measurements only the unquenched source of the previous set was measured. The same analysis procedure described for 63Ni in the previous section was applied to 99Tc. In Fig. 5 the activity concentration of 99Tc as a function of different tc values (varying between 20 and 240 ns) and for two tdead values (10 and 50 μs) is shown (for kB¼kB0) as obtained by using the ENEA software analysis code. A TDCR parameter of 0.9419 was measured for 99Tc using the new portable TDCR counter, compared to 0.9709 obtained for the same source using the Hidex system. In Table 2 the 99Tc activity concentration (for kB¼kB0) measured by the portable TDCR system with tc ¼120 ns and tdead ¼50 μs is compared to the values obtained by using the Hidex counter and the CIEMAT/NIST method, by using the same kB0 value and tc ¼40 ns for the Hidex counter and tc ¼ 18 ns for the Tricarb counter. The kB0 value selected for this measurement is supported by a study carried out at ENEA-INMRI as described by Capogni and Antohe (2014). The uncertainty budget for 63Ni and 99Tc activity measurements performed with the new portable TDCR counter is reported in Table 3. In this table the influence of the kB parameter on the uncertainty budget was estimated by taking into account the variation of the efficiencies εT and εD as function of this parameter for a range of values very close to the selected kB0 value, while the contribution of the ionization quenching was estimated by taking into account the effect on the activity concentration (for kB¼kB0) due to the variation of the TDCR parameter obtained by measuring different quenched samples of the same radioactive solution.

The same set of experimental data was analyzed by the two software codes developed independently by CAEN and ENEA and by setting the same parameter for tc and tdead. Deviations Δ(%)¼ 100n(1 aENEA/aCAEN) equal to 0.06% and 0.03% were observed for 63 Ni and 99Tc respectively. A similar investigation was carried out Table 1 63 Ni activity concentration and its uncertainties (k ¼1) on reference time (kB ¼0.011 cm MeV 1, tc ¼ 140 ns, and tdead ¼50 μs). LSC system

LSC method

a (kBq g 1)

u(a) (kBq g 1)

u(a) (%)

Portable TDCR counter Hidex counter Tricarb counter

TDCR TDCR CIEMAT/NIST

30.38 30.63 30.38

0.21 0.25 0.18

0.68 0.80 0.58

99

with the same device for a 90Sr–90Y source and was reported by Mini et al. (2014). The typical uncertainty on the Δ value is 0.01%, meaning that the deviations observed in activity results between the two software codes are lower than 0.1%; this little difference is probably due to the different algorithms applied in the two programs developed for TDCR analysis to manage the dead-time and the coincidences between the three channels.

5. Measurements with the PSD technique The new portable TDCR device was also used for preliminary application of the PSD technique to a source containing a mixture of 241Am and 90Sr prepared by the radiochemistry laboratory of the ENEA-INMRI in a glass vial with 10 mL of UG. In this case, the TDCR detector was directly linked to the CAEN digitizer DT5720B without any pre-amplifier between this device and the PMTs. The same setting parameters used above for the discrimination level Table 2 99 Tc activity concentration and its uncertainties (k ¼ 1) on reference time (kB ¼ 0.011 cm MeV 1, tc ¼120 ns, and tdead ¼50 μs). LSC system

LSC method

a (kBq g 1)

u(a) (kBq g 1)

u(a) (%)

Portable TDCR counter Hidex counter Tricarb counter

TDCR TDCR CIEMAT/NIST

56.53 56.56 56.70

0.23 0.22 0.28

0.40 0.39 0.49

Table 3 Uncertainty budget (k ¼ 1) for 63Ni and 99Tc activity measurements carried out with the new portable TDCR system (kB¼ 0.011 cm MeV 1 and tdead ¼50 μs).

4.3. Comparison of the current analysis programs

Fig. 5.

5

Uncertainty component (%)

63

Counting statistics Weighing Dead time Background Counting time Adsorption Impurities Influence of kB parameter Input parameter and statistical model Ionization quenching Decay-scheme parameters Half-life PMT asymmetry Coincidence resolving time Combined uncertainty

0.10 0.05 0.04 0.01 0.03 0.03 0.05 0.40 0.30 0.20 0.01 0.20 0.30 0.15 0.68

Ni

99

Tc

0.10 0.05 0.02 0.01 0.03 0.03 0.05 0.10 0.20 0.10 0.01 0.20 0.20 0.05 0.40

Tc activity concentration as a function of different values of tc (kB ¼0.011 cm MeV 1).



6

Fig. 6. PSD parameter as a function of the Qlong-charge values for a

and charge sensitivity of the three channels were applied. A Short Gate of 24 ns and a Long Gate of 80 ns were imposed to record the values of the Qshort and Qlong-charges. In Fig. 6 the bi-dimensional plot of the PSD parameter as a function of the Qlong charge value is shown. In this figure it is clear that the alphas emitted by the 241 Am source are well separated from the beta particles emitted by the 90Sr source in equilibrium with its 90Y daughter. By selecting the area of the bi-dimensional plot due to the 90Sr–90Y β-emissions with a graphical cut it is possible to perform the TDCR analysis on these selected events. Further investigations on this subject are still in progress.

6. Conclusions and outlook The new portable TDCR system developed at ENEA-INMRI and equipped with high performance square miniature PMTs and both desktop-type CAEN digitizers DT5720 and DT5720B were used to measure the activity concentrations of 63Ni and 99Tc with uncertainties lower than 1%. A new software code was implemented at ENEA-INMRI in CERN ROOT environment for off-line TDCR analysis. The PSD algorithm was implemented in this code and tested to discriminate alpha and beta particles emitted by a source composed of a mixture of 241Am and 90Sr standardized solutions. These results open new interesting perspectives in Italy for activity measurements of beta and alpha emitters for which the new device could be used as a traveling instrument for in-situ measurements. This is particularly useful in many applications of the nuclear energy industry and in the field of nuclear medicine.

Acknowledgments This work was supported by EMRP in the framework of the EMRP joint research project (JRP) ENG08 Metrofission. This JRP was carried out with funding by the European Union. The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union. The authors are indebted to Freda van Wyngaardt from ANSTO for the fruitful discussion in LSC measurements and for the English language revision of the manuscript. They wish to thank Philippe Cassette from LNHB-CEA, for the very useful suggestions and discussions on the TDCR method and for providing the code TDCR07c. The authors are grateful to Maria Letizia Cozzella from ENEA-INMRI for supplying the radioactive sources and to the ENEA technical staff who contributed to this work: Massimo Pagliari and Sergio Mancini for the support in

241

Am-90Sr/90Y source.

the mechanical and electrical parts of the TDCR device, and Aldo Fazio for the gamma impurity check performed on the β-emitting mother solutions.

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A portable TDCR system.

Construction and implementation of a TDCR system at ENEA.

Bilateral comparison between PTB and ENEA to check the performance of a commercial TDCR system for activity measurements.

A miniature TDCR system dedicated to in-situ activity assay.

Set-up of a new TDCR counter at IRA-METAS.

A prototype expert system for fishway design.

A portable target controlled propofol infusion system.

A prototype beam delivery system for the proton medical accelerator at Loma Linda.

A Prototype for Executable and Portable Electronic Clinical Quality Measures Using the KNIME Analytics Platform.

Theophylline analysis at the chest clinic--comparison of a portable versus conventional system.

First TDCR measurements at low energies using a miniature x-ray tube.

Performance of a prototype fluoroscopic radiotherapy imaging system.

PSAMM: A Portable System for the Analysis of Metabolic Models.

A Prototype SSVEP Based Real Time BCI Gaming System.

PORTER: a Prototype System for Patient-Oriented Radiology Reporting.

A portable, disposable system for negative-pressure wound therapy.

A Portable Farmland Information Collection System with Multiple Sensors.

A full digital approach to the TDCR method.

A Practical and Portable Solids-State Electronic Terahertz Imaging System.

The smartphone brain scanner: a portable real-time neuroimaging system.

A portable system for studying discrete-trial group choice.

Portable shade structure use at a youth soccer camp.

Preliminary evaluation of a personal healthcare system prototype for cognitive eRehabilitation in a living assistance domain.

Evaluation of a prototype ration aimed at increasing caloric intake in a field environment.