Portable diagnostic package for Thomson scattering and optical emission spectroscopy on Princeton field-reversed configuration 2 (PFRC 2)

An Advanced Research Projects Agency-Energy funded diagnostic system has been deployed to the Princeton field-reversed configuration 2 (PFRC-2) device, located at Princeton Plasma Physics Laboratory. The Portable Diagnostic Package (PDP), designed at Oak Ridge National Laboratory, allows for the measurement of Thomson Scattering (TS) for electron density and temperature and Optical Emission Spectroscopy (OES) for ion temperature, impurity density, and ion velocity. A tunable spectrometer on the PDP with three gratings provides the flexibility to measure low (1 eV) and high (1000 eV) electron temperature ranges from TS. Additionally, using a second spectrometer, the OES diagnostic can survey light emission from various ion excitation levels for wide wavelength ranges. The electron density (<2 × 10¹⁹ m^-3) of plasmas generated in PFRC-2 has been below the PDP TS discrimination threshold, which has made TS signal detection challenging against a high-background of laser stray light. The laser stray light was iteratively reduced by making modifications to the entrance and exit geometry on PFRC-2. Rayleigh scattering experiments on PFRC have yielded the TS discrimination sensitivity to be >1 × 10²⁰ m^-3 for the PDP. A recently implemented narrow-band notch spectral filter that masks the second harmonic 532 nm Nd:YAG laser wavelength has increased the system's TS light discrimination sensitivity 65 times compared to the instance when the notch filter was not implemented. The hardware implementation including design changes to the flight tubes and Brewster windows will be discussed, along with results from Rayleigh and rotational Raman scattering sensitivity analyses, which were used to establish a quantitative figure of merit on the system performance. The Raman scattering calibration with the notch filter has improved the PDP electron density threshold to 1 ± 0.5 × 10¹⁸ m^-3.

Implementation of a portable diagnostic system for Thomson scattering measurements on an electrothermal arc source

To fulfill the increasing needs of diagnostic support for researchers in plasma technology, a portable diagnostic package (PDP) equipped for both laser Thomson scattering (TS) and optical emission spectroscopy has been designed and constructed at Oak Ridge National Laboratory (ORNL), aiming to measure the temperature and number density of electrons and temperatures of ions in plasma devices. The PDP has been initially implemented on a high density and low temperature electrothermal arc source (ET-arc) at ORNL to test its TS capability. TS from the plasmas in the ET-arc has been obtained using the PDP. The electron temperature and number density were determined from TS spectra. These results were then compared to measurements from previous studies on the ET-arc. The TS diagnostic measured 0.8 ± 0.1, 1.3 ± 0.2, and 0.7 ± 0.1 eV and (4.4 ± 0.5) × 10²¹, (5.9 ± 0.7) × 10²¹, and (4.3 ± 0.5) x 10²¹ m^-3, respectively, from three lines of sight that transect the plasma column.

Introducing Clinical Pathology Course to Fourth Year Medical Students as a Bridge between Pre-clinical and Clinical Medical Sciences

There isn't any vertical integration of pre-clinical and clinical sciences subjects in the existing Kathmandu University MBBS curriculum. Many of the graduates are not able to correlate the clinico-pathological aspects of various diseases as a result the rational use of investigations for diagnosing various diseases is compromised. There are few published examples of implementation of pathology instruction courses during the clinical years of medical training but it is not universally practiced. This lack of exposure to pathology may lead to poor understanding of laboratory testing and the role of pathologists in patient care. To set and implement an exemplary vertical integration of pre-clinical science with clinical science. A 12 credit hours clinical pathology education course comprising clinical hematology, cytopathology and histopathology was developed. Students belonging from the ongoing fourth year MBBS course of Birat Medical College were enrolled in the course. All of the interactive lecture sessions were delivered via an e-learning interface, using the Zoom platform as the main teaching methods. Evaluation of students' achievement of learning objectives was conducted through distributing pre and post-test online multiple-choice questionnaires. Chi-square tests were used to compare the variables between pre-test and post-test questionnaire responses. Results suggested that the designed clinical pathology course is valuable. The pretest and post-test questionnaire responses revealed the positive impact regarding the importance of introducing clinical pathology courses within the clinical year of MBBS undergraduate curriculum. Response rate to the online session was 100%. The point of agreement between the pre-test and post-test questionnaire responses were highly achieved after intervention of the clinical pathology course. A statistically significant result (p < 0.05) between all of the pre-test and post-test questionnaire responses was noted. There was a strong positive recommendation for incorporating clinical laboratory medicine courses within the MBBS clinical science curriculum. The improvement observed among fourth-year MBBS students on learning the importance of clinical pathology courses was encouraging. This experience thus contributed to set and implement an exemplary vertical integration of pre-clinical science with clinical science.

Design and implementation of a portable diagnostic system for Thomson scattering and optical emission spectroscopy measurements

A diagnostic system, which has a design goal of high-portability, has been designed at Oak Ridge National Laboratory (ORNL). This project aims at providing measurements of key plasma parameters (n_e, T_e, n_i, T_i) for fusion-relevant devices, utilizing Thomson scattering (TS) and optical emission spectroscopy (OES). The innovative design employs mostly commercial off-the-shelf instrumentation and a traveling team of researchers to conduct measurements at various magnetic-confinement plasma devices. The TS diagnostic uses a Quantel Q-smart 1500 Nd:YAG laser with a 2ω harmonic generator to produce up to 850 mJ of 532 nm laser pulses at 10 Hz. Collection optics placed at the detection port consists of an 11 × 3 optical fiber bundle, where the TS diagnostic uses an 11 × 1 subset array of the fibers, the OES diagnostic uses another 11 fibers, and the remaining fibers are available to the host institution. The detection system is comprised of two separate IsoPlane-320 spectrometers with triple-grating turrets of various line spacing and two PI-MAX 4 intensified CCD detectors, used simultaneously to measure a broad range of ion, impurity, and electron parameters. The self-contained diagnostic package also includes a data processing and storage system. The design and initial implementation of the TS-OES diagnostic system are described. The experiments from the proof-of-principle operation of the portable package on a high density (∼2.5 × 10²² m^-3) and low-temperature (∼5 eV) electrothermal arc source at ORNL are also discussed.

Dual-pass upgrade to the Thomson scattering diagnostic on the Prototype-Material Plasma Exposure eXperiment (Proto-MPEX)

The Thomson scattering (TS) diagnostic on the Prototype-Material Plasma Exposure eXperiment has been upgraded to measure electron temperature (T _e ) and density (n _e ) simultaneously at two axial locations. After the first pass through the vacuum vessel, the exiting laser beamline is re-collimated in the atmosphere and rerouted into the vacuum vessel for the second pass. The upgrade will help diagnose axial T _e and n _e gradients between the "central chamber" and the target region which are located 1 m and 2.5 m, respectively, downstream from the Helicon radio-frequency source. The TS measurements have given T _e ≈ 4-15 eV and n _e ≈ 2-4 × 10¹⁹ m^-3 at the central chamber and T _e ≈ 1-2 eV and n _e ≈ 1-2 × 10¹⁹ m^-3 at the target region. The upgrade also increases the number of sampling points at the target region from 3 fibers to 5 fibers, measuring 3 cm radially across the plasma column, and 25 fibers in the central chamber, radially spanning 8 cm. The intensified CCD camera is double triggered for each laser pulse in order to measure (1) the TS and laser stray light and (2) the plasma background light that contains nuisance emission lines and bremsstrahlung. Subtracting the background light from the TS photons improves the temperature and density measurements. Details of the diagnostic setup, axial and radial measurements, and areas for further optimization are discussed.

Histopathologic Analysis of Pancreaticoduodenectomy Specimen

INTRODUCTION

Whipple's Pancreaticoduodenectomy has increasingly been used as an appropriate resectional procedure for tumors of the periampullary region which are pancreatic, periampullary, ampullary and biliary tumors. Our aim was to study the distribution and histopathologic features of these tumors and to examine local trends of periampullary neoplasms resected with a PD.

METHODS

A descriptive study was conducted in the department of Pathology, Kathmandu Medical College Teaching Hospital from July 2013 to June 2016.

RESULTS

Thirty five patients underwent Whipple's Pancreaticoduodenectomy procedure during a period of 36 months from July 2013 to June 2016. Malignant tumor was present in 31 (88.57%) cases where as four cases (11.43%) harboured benign lesions. Periampullary mixed carcinoma was the predominant tumor (34.28%) followed by periampullary duodenal (20%), ampullary (14.28%), pancreatic adenocarcinoma (11.42%) and distal cholangiocarcinoma (5.71%). There was no significant difference in tumor size among periampullary, ampullary, pancreatic and biliary carcinomas. Ampullary carcinomas were predominantly well differentiated (80%) where as the other tumors were mostly moderately differentiated. Lymphovascular and perineural invasion varied in different tumor types. Four pancreatic adenocarcinomas showed lymphovascular and perineural invasion. Adequate surgical margin clearance was achieved in most of the cases except in one case each of periampullary duodenal carcinoma and distal cholangiocarcinoma and two cases of pancreatic adenocarcinoma..

CONCLUSIONS

Pancreaticoduodenectomy specimen requires thorough histopathological evaluation. Pathologists should also be aware of possibility of a benign diagnosis in PD specimens which have been resected presuming malignancy based on clinical judgement and radiological data.