High wavelength-resolution Bragg-edge/dip transmission imaging instrument with a supermirror guide-tube coupled to a decoupled thermal-neutron moderator at Hokkaido University Neutron Source

2017 ◽

Vol 18 (1) ◽

pp. 1 ◽

Cited By ~ 1

Author(s):

Edi Trijono Budisantoso ◽

Syarip Syarip

Keyword(s):

Neutron Flux ◽

Thermal Neutron ◽

Neutron Source ◽

Neutron Beam ◽

Thermal Neutron Flux ◽

Prompt Gamma ◽

Basic Design ◽

Neutron Moderator ◽

Sample Chamber ◽

Beam Stopper

ABSTRAK ANALISIS RANCANGAN DASAR SISTEM PGNAA MENGGUNAKAN SUMBER NEUTRON DARI BEAMPORT REAKTOR KARTINI. Telah dilakukan perancangan dasar sistem PGNAA menggunakan salahsatu beamport reaktor Kartini sebagai sumber neutron. Moderator neutron ditempatkan pada ujung kolom berkas neutron untuk membuat berkas neutron menjadi termal. Berkas diarahkan menuju ruang sampel PGNAA dengan menggunakan kolimator yang berfungsi sebagai penyaring berkas neutron sejajar. Pada penggal kolimator yang berpotongan dengan jendela beamport dipasang neutron beam shutter untuk menutup berkas neutron apabila tidak digunakan untuk PGNAA. Beam stopper dipasang dibelakang ruang sampel PGNAA untuk menangkap berkas neutron yang lolos. Perhitungan sifat neutronik dilakukan untuk memilih bahan material yang memenuhi syarat fungsi sebagai sub-komponen PGNAA dan menentukan ukuran geometrinya. Dari hasil perhitungan diperoleh data bahan yang baik untuk moderator yaitu grafit, bahan kolimator adalah aluminium, bahan beam shutter dan beam stopper adalah komposit boraks-parafin. Panjang moderator 90 cm, panjang kolimator 173 cm dengan tetapan kolimasi D/L=0,015, tebal beam shutter dan beam stopper masing-masing 22 cm dan 30 cm. Dipasang perisai gamma dan perisai neutron untuk menutup berkas neutron keluar dari sela dinding dalam beamport dan didnding luar kolimator. Bahan perisai tersebut dibuat dari komposit boraks parafin 25% berat dan timbal yang masing-masing panjangnya 50 cm dan 30 cm. Hasil analisis menunjukkan bahwa dari fluks neutron awal pada beamport bagian dalam sebesar 1,5.1012 n/cm2s dapat menghasilkan fluks neutron termal di ruang sampel PGNAA 1,76.108 n/cm2s dengan arus neutron termal 9,29.108 n/s. Nilai fluks neutron termal tersebut memenuhi persyaratan untuk suatu sistem PGNAA yaitu berada pada orde 106 s/d 108 n/cm2s. Kata Kunci : PGNAA, rancangan dasar, prompt-gamma, analisis aktivasi, neutron-termal, beamport reaktor ABSTRACT BASIC DESIGN ANALYSIS OF PGNAA SYSTEM USING NEUTRON SOURCE FROM BEAMPORT OF KARTINI REACTOR. A basic design of PGNAA system using one of reactor beamports of Kartini reactor as a neutron source have been carried out. Neutron moderator is placed at the inner end of beamport column to make thermal neutron beam. A neutron beam directed to PGNAA counting chamber by using collimator as a filter to make parallel neutron beam. At the midle of collimator intersect with beamport window, neutron beam shutter is mounted to close when not in use for PGNAA. Beam stopper mounted behind the sample chamber of PGNAA to capture neutron beam that passes from the sample chamber. Calculation of neutronic properties of materials was done to choose the material that meet the functional requirements of PGNAA and to determine the geometry size. Based on the calculational results obtained that good material for moderator is graphite, aluminum as beam collimator, and beam shutter or stopper is made from borax-paraffin composite. The moderator length is 90 cm and collimator length is 173 cm with collimation constant D / L = 0,015. Beam shutter and beam stopper thickness are 22 cm and 30 cm respectively. Gamma and neutron shield are added surrounding beam colimator to shield the radiation out from the pitch between collimator and beamport wall. The shield material made from composite of parrafin 25 w % borax, and lead with the length of 50 cm and 30 cm respectively. The analysis result shows that from the neutron flux of 1,5.1012 n/cm2s at the inner side of beamport, can generate thermal neutron flux at the PGNAA sample chamber of 1,76.108 n/cm2s with the thermal neutron current of 9,29.108 n/s. This thermal neutron flux meet the requirement for a PGNAA system i.e. in the order of 106 to 108 n/cm2s. Keywords : PGNAA, basic design, prompt-gamma, activation analysis, thermal neutron, reactor beamport

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Frame overlap Bragg edge imaging

Scientific Reports ◽

10.1038/s41598-020-71705-4 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Matteo Busi ◽

Jan Čapek ◽

Efthymios Polatidis ◽

Jan Hovind ◽

Pierre Boillat ◽

...

Keyword(s):

Short Pulse ◽

Large Fraction ◽

Strain Mapping ◽

Neutron Sources ◽

Spatially Resolved ◽

Transmission Imaging ◽

Imaging Detector ◽

Wavelength Resolution ◽

Order Of Magnitude ◽

High Wavelength

Abstract Neutron Bragg edge imaging enables spatially resolved studies of crystalline features through the exploitation and analysis of Bragg edges in the transmission spectra recorded in each pixel of an imaging detector. Studies with high spectral resolutions, as is required e.g. for high-resolution strain mapping, and with large wavelength ranges have been largely reserved to pulsed neutron sources. This is due to the fact, that the efficiency for high wavelength resolution measurements is significantly higher at short pulse sources. At continuous sources a large fraction of the available neutrons must be sacrificed in order to achieve high wavelength resolution for a relevant bandwidth e.g. through a chopper system. Here we introduce a pulse overlap transmission imaging technique, which is suited to increase the available flux of high wavelength resolution time-of-flight neutron Bragg edge imaging at continuous neutron sources about an order of magnitude. Proof-of-principle measurements utilizing a chopper with a fourfold repeated random slit distribution of eight slits were performed at a thermal neutron beamline. It is demonstrated, that disentanglement of the overlapping pulses is achieved with the correlation theorem for signal processing. Thus, the Bragg edge pattern can be reconstructed from the strongly overlapping Bragg edge spectra recorded and the results demonstrate the feasibility of the technique.

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