Louisiana Accelerator Center

: Development of a biosafety level-2 facility for irradiation of biological cells using MeV ions
Description: The development of a facility for irradiation of murice and primate tissue presents several challenges. First, extremely low fluences (10⁶-10¹¹ ions c
Show moreThe development of a facility for irradiation of murice and primate tissue presents several challenges. First, extremely low fluences (10⁶-10¹¹ ions cm⁻²) are required to deliver doses of 1 mGy - 50 Gy using MeV proton. Second,the tissues, particularly from non-human primate, may be infectious to humans. Third, protection of irradiated tissue samples from contamination by mold and bacteria is critical. Here we present an ultra-low flux irradiation facility and associated fluence control for biological cell and tissue irradiation under sterile biosafety level 2 (BSL-2) conditions suitable for use with low energy (1-3.4 MeV) protons. The operation is demonstrated using murine astocytes.
Submitted 9 February 2019, Received in revised form 28 February 2019, Accepted 4 March 2019
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Subject: Ultra low-flux irradiation
Type of Resource: text

: The Electronic Accelerator: A versatile tool
Description: Electrostatic accelerators have been at the forefront of modern technology since 1932, when Sir John Cockroft and Ernest Walton developed the first ac
Show moreElectrostatic accelerators have been at the forefront of modern technology since 1932, when Sir John Cockroft and Ernest Walton developed the first accelerator. Although the electrostatic accelerator field is over 90 years old, the field and the number of accelerators is growing more rapidly than ever. This book provides a collection of the basic science and technology that underlies the electrostatic accelerator field so it can serve as a handbook, reference guide, and textbook for accelerator engineers, students, and researchers in the field.
Book
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Type of Resource: text

: Fabrication of high-transmission microporous membranes by proton beam writing-based molding technique
Description: Porous membranes are widely used as filters in a broad range of micro and nanofluidic applications, e.g. organelle sorters, permeable cell growth subs
Show morePorous membranes are widely used as filters in a broad range of micro and nanofluidic applications, e.g. organelle sorters, permeable cell growth substrates, and plasma filtration. Conventional silicon fabrication approaches are not suitable for microporous membranes due to the low mechanical stability of thin film substrates. Other techniques like ion track etching are limited to the production of randomly distributed and randomly orientated pores with non-uniform pore sizes. In this project, we developed a procedure for fabricating high-transmission microporous membranes by proton beam writing (PBW) with a combination of spin-casting and soft lithography. In this approach, focused 2 MeV protons were used to lithographically write patterns consisting of hexagonal arrays of high-density pillarsof few μm size in a SU-8 layer coated on a silicon wafer. After development, the pillars were conformably coated with a thin film of poly-para-xylylene (Parylene)-C release agent and spin-coated with polydimethylsiloxane (PDMS). To facilitate demolding, a special technique based on the use of a laser-cut sealing tape ring was developed. This method facilitated the successful delamination of 20-μm thick PDMS membrane with high-density micropores from the mold without rupture or damage.
Received 26 July 2016 Received in revised form 13 April 2017 Accepted 19 April 2017 Available online 4 May 2017
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Subject: proton beam writing
Type of Resource: text

: Inexpensive Simple Extraction of Trace PAHs from Water using PS- DVB Monolithic Beads
Description: A new simple and sensitive analytical technique based on polystyrene-divinyl benzene (PS-DVB) monolithic bead extraction followed by gas chromatograph
Show moreA new simple and sensitive analytical technique based on polystyrene-divinyl benzene (PS-DVB) monolithic bead extraction followed by gas chromatography–mass spectroscopic detection (GC-MS) was developed for the determination of polycyclic aromatic hydrocarbons (PAHs) in water. The PS-DVB monolithic bead was fabricated and used as the adsorbent. The experimental parameters controlling the performance of the bead extraction were optimized. Calibration curves showed excellent linear fits, with r2 >0.995 for all PAHs in the 2–30,000 ng mL-1 range. The limits of detection (LODs) ranged from 0.01 to 0.47 ng mL-1. Recoveries of the PAHs in environmental water samples spiked at a concentration of 500 ng mL-1 were 72-109%, while they were 69-114% for water spiked at 20 ng mL-1. Both intraday and interday repeatabilities were high, with RSDs for 16 PAHs spiked standard solutions being less than 10%. The present study indicated that the proposed method is well suited for the quantification of PAHs in environmental and drinking water samples.
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Geographic Area: Thailand
Subject: Analytical chemistry
Date Issued: 2018-09-16
Type of Resource: text

: Investigation of mercury pathways from dental amalgam by micro-PIXE
Description: Mercury amalgams are still widely used in dentistry in many countries. There is considerable concern about uptake of Hg in both the patient and enviro
Show moreMercury amalgams are still widely used in dentistry in many countries. There is considerable concern about uptake of Hg in both the patient and environment. It is an interesting question if the pathway is by Hg diffusion through the tissue of the tooth or dissolution in saliva or direct evaporation through inhaled air into the lung. Our previous study [1] of a high-Cu amalgam showed no evidence of diffusion through the enamel. However, a compositional change was observed on the biting surface of the amalgam which is indicative of tribochemical changes. To investigate if the above observation was true for other types of amalgam, 17 adult teeth with amalgam obtained as operation-waste from dental clinics. The samples were embedded and sliced into 1mm sections in the coronal plane of the tooth using a low/speed diamond saw with water-based cooling. Subsequently, the slices were mechanically polished in such way that polishing debris was swept away from the sample. Micro-PIXE with 2 MeV protons was carried out in vacuum using a standard Oxford –triplet configuration. In common with our previous study [1], sharp interfaces between the enamel and amalgam were observed with no strong evidence for Hg diffusion in the enamel. Little evidence exists consistent with the presence of tribochemical alteration by mastication. However, Zn was observed to be localized at different sites in the amalgam/enamel interface.
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Type of Resource: text

: Investigations of minor elements in early aluminium artefacts
Description: Study of the minor and trace element contents in the composition of early aluminium is interesting from a cultural history perspective because it can
Show moreStudy of the minor and trace element contents in the composition of early aluminium is interesting from a cultural history perspective because it can provide information on the evolution of aluminium smelting practice. A range of aluminium artefacts from the Swiss National Museum and the Lausanne Historical Museum, Switzerland, have been characterised with regard to their minor and trace element composition. This was performed using external beam Particle Induced X-ray Emission (PIXE) with 1 MeV protons and a portable X-ray fluorescence system. The concentration of Mn and Pb was significantly higher for artefacts produced by the amalgam process which confirms studies reported by others.
Received 29 October 2017; Received in revised form 29 July 2018; Accepted 16 August 2018 Available online xxx 0168-583/ © 2018.
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Subject: Aluminum artefacts
Date Issued: 2018-08-16
Type of Resource: text

: Irradiation effects of MeV protons on dry and hydrated Brassica rapa seeds
Description: Although space radiation is a known risk for space travel and eventual colonization of Moon or Mars, relatively few data exist on radiation effects on
Show moreAlthough space radiation is a known risk for space travel and eventual colonization of Moon or Mars, relatively few data exist on radiation effects on potential crop plants. We studied 𝘉𝘳𝘢𝘴𝘴𝘪𝘤𝘢 𝘳𝘢𝘱𝘢 to assess the tolerance of seeds and seedlings to radiation by exposing dry and hydrated 𝘉. 𝘳𝘢𝘱𝘢 seeds to 1, 2 and 3 MeV proton ions of various fluences and examined the effect on germination and root growth. Modeling penetration depth with SRIM code indicated that the applied energy was insufficient to penetrate the seeds; therefore, all energy was deposited into the tissue. Subsequent germination varied based on the incident ion energy and fluence (dose). Dry and hydrated seeds germinate after ion fluence (10¹³ ions cm⁻²) irradiation, but the germination percentage decreased with increasing fluence for ions that could penetrate the seed coat (> 1 MeV). Despite their greater volume and mass, hydrated seeds were more sensitive to irradiation than dry seeds. Damage of the seed coat after irradiation led to faster germination and initial seedling growth. Our results suggest that the seed coat represents a valuable natural radiation protection and that low energy protons, the prevailing solar radiation, are suitable for studying radiation effects in seeds and plants.
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Subject: Seeds
Type of Resource: text

: MeV ion exposure behavior of PMMA resist polymer studied by synchrotron light spectroscopies
Description: The behaviour of poly-(methyl methacrylate) (PMMA) resist exposed with 2 MeV¹ H⁺ and 6 MeV¹² C³⁺ ions has been investigated by using the photo-electro
Show moreThe behaviour of poly-(methyl methacrylate) (PMMA) resist exposed with 2 MeV¹ H⁺ and 6 MeV¹² C³⁺ ions has been investigated by using the photo-electron spectroscopy (PES) and X-ray absorption spectroscopy (XAS) techniques. Preliminary PES results were difficult to analyse without special precautions to counteract surface charging. XAS was on the other hand almost insensitive to the effects of surface charging. XAS investigations of the bonding in the near surface and deeper in PMMA revealed significant changes of the bonding of carbon atoms at fluences correspond to clearing (positive resist mode) and cross-linking (negative resist mode). In the clearing fluence regime the C=C bonds increase in the surface and at greater depths which is consistent with our earlier work with Raman spectroscopy. In the high fluence regime where cross-linking takes place, a reduction of C-O and C=O bonding is seen which might be indicative that the cross linking is associated with side-chain scission.
Received 31 August 2016 Received in revised form 16 November 2016 Accepted 23 January 2017 Available online xxxx
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Subject: MeV ion beam lithography
Type of Resource: text

: Micro-PIXE study of metal loss from dental amalgam
Description: Mercury amalgams have been a topic of controversy ever since their introduction over 150 years ago as a dental material. An interesting question is if
Show moreMercury amalgams have been a topic of controversy ever since their introduction over 150 years ago as a dental material. An interesting question is if metals are released from the amalgam into the enamel and dentine tissue. To elucidate this PIXE mapping was used to investigate metal redistribution in an extracted molar tooth with a ∼30 year old high-Cu content amalgam filling. The tooth was sectioned and polished, and elemental mapping carried out on the amalgam/enamel, bulk amalgam and the wear surface of the amalgam. As expected, the amalgam was multiphase amalgam comprising of Cu-rich and Ag-rich grains with non-uniform distribution of Hg. The amalgam/dentine interface was clearly defined with amalgam elements on one side and C and P from hydroxyapatite on the other side with evidence of only slight interface corrosion. The peaks for Cu Hg and Zn were isolated from interfering signals with concentrations in the enamel tissue, observed to be at, or below the method detection limit. The proximity in energy of the Sn Lα and Ca Kα, peaks and the background on the Hg Mα gave signal overlap which increased the MDL for these elements. Remarkably, a course grain texture in the amalgam was observed just below the biting surface of the amalgam which might be associated with tribochemical processes from mastication. This coupled with the clear absence of the amalgam metals from tooth tissue, even in close proximity to the interface, suggests that for this sample, release of Hg occurred via erosion or dissolution in saliva.
Received 30 August 2016 Received in revised form 11 January 2017 Accepted 13 January 2017 Available online 27 January 2017
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Subject: PIXE
Type of Resource: text

: Post-focus expansion of ion beams for low fluence and large area MeV ion irradiation: Scaling from the single-event to the system level in human brain tissue and electronics devices.
Description: Irradiation with ~ 3 MeV proton fluences of 10⁶ - 10⁹ protons cm⁻² have been applied to study the effects on human brain tissue corresponding to singl
Show moreIrradiation with ~ 3 MeV proton fluences of 10⁶ - 10⁹ protons cm⁻² have been applied to study the effects on human brain tissue corresponding to single-cell irradiation doses and doses received by electronic components in low-Earth orbit. The low fluence irradiations were carried out using a proton microbeam with the post-focus expansion of the beam; a method developed by the group of Breese [1]. It was found from electrophysiological measurements that the mean neuronal frequency of human brain tissue decreased to zero as the dose increased to 0 to 1050 Gy. Enhancement-mode MOSFET transistors exhibited a 10% reduction in threshold voltage for 2.7 MeV proton doses of 10Gy while a NPN bipolar transistor required ~800 Gy to reduce the h𝒻ₑ by 10% which is consistent the expected values.
Received 30 December 2016, Accepted 23 January 2017, Available online 22 February 2017
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Subject: MeV broad beam ion irradiation
Type of Resource: text

: Time detector design for Time-of-Flight Elastic Recoil Detection Analysis (ToF-E ERDA) revisited
Description: Time-of-flight-energy elastic recoil detection analysis (ToF-E ERDA) is a uniquely powerful thin-film analytical technique because it can be used to m
Show moreTime-of-flight-energy elastic recoil detection analysis (ToF-E ERDA) is a uniquely powerful thin-film analytical technique because it can be used to measure simultaneously the depth distributions of all elements in a thin-film sample. The basic design of the time detectors which are generally based on the electron mirror has not changed significantly over 25 years or so. A classic electron optical study has been made to elucidate the factors that limit the time resolution of electron mirror time pick off detectors and how they are interrelated. Degradation of the time resolution is mainly associated with the electron divergence from an ideal straight trajectory and variations in the propagation of electromagnetic pulses over the anode surface. A set of equations that can be used to optimise time detector design are presented along with a new configuration that has an expected time resolution of 40 ps fwhm and overcomes most of the drawbacks of the conventional configuration.
10 November 2017; Received in revised form 6 November 2018; Accepted 7 November 2018
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Subject: ToF-E ERDA
Type of Resource: text

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