A compact and portable gamma-ray spectrometer (GRASP) for inertial confinement fusion and basic science experiments.

A compact and portable gamma-ray spectrometer has been designed to diagnose different components of the inertial confinement fusion-relevant γ-ray spectrum with energies between ∼3.7-17.9 MeV. The system is designed to be as compact as possible for convenient transportation and fielding in diagnostic ports on the OMEGA laser, the National Ignition Facility, and other photon-source facilities. The system consists of a conversion foil for Compton scattering in front of four magnetic spectrometer "arms," each covering a different energy range and constructed out of cylindrical permanent magnet Halbach arrays. Monte Carlo simulations have been used to optimize and assess the performance of the conversion foil, and COSY INFINITY ion-optical simulations have been used to optimize the spectrometer magnets. The performance of the design is assessed for a simulated direct-drive γ-ray spectrum. Spanning its total γ-ray energy bandwidth and using a 1.7 mm thick boron conversion foil, the system's total energy resolution and efficiency are ∼15.8%-4.5% and 5.4 × 10-7-3.7 × 10-7e-/γ, respectively, with room for improvement. Spectral γ-ray measurements will provide guidance to the inertial confinement fusion program toward achieving high-energy gain relevant to inertial fusion energy and enable new measurement capabilities for basic discovery science.

The next-generation magnetic recoil spectrometer (MRSnext) on OMEGA and NIF for diagnosing ion temperature, yield, areal density, and alpha heating.

The next-generation magnetic recoil spectrometer (MRSnext) is being designed to replace the current MRS at the National Ignition Facility and OMEGA for measurements of the neutron spectrum from an inertial confinement fusion implosion. The MRSnext will provide a far-superior performance and faster data turnaround than the current MRS systems, i.e., a 2× and 6× improvement in energy resolution at the NIF and OMEGA, respectively, and 20× improvement in data turnaround time. The substantially improved performance of the MRSnext is enabled by using electromagnets that provide a short focal plane (12-16 cm) and unprecedented flexibility for a wide range of applications. In addition to being able to measure neutron yield, apparent ion temperature, areal density, and plasma-flow velocity over a wide range of yields, the NIF MRSnext will be able to directly, uniquely assess the alpha heating of the fuel ions through measurements of the alpha knock-on tail in the neutron spectrum. The goal is to implement a radiation-hard electronic detection system capable of providing rapid data acquisition and analysis. The development of the MRSnext will also set the foundation for the more advanced, time-resolving MRSt and serve as a testbed for its implementation on the NIF.

Characterization of the image plate multi-scan response to mono-energetic x-rays.

Image plates (IPs), or phosphor storage screens, are a technology employed frequently in inertial confinement fusion (ICF) and high energy density plasma (HEDP) diagnostics because of their sensitivity to many types of radiation, including, x rays, protons, alphas, beta particles, and neutrons. Prior studies characterizing IPs are predicated on the signal level remaining below the scanner saturation threshold. Since the scanning process removes some signal from the IP via photostimulated luminescence, repeatedly scanning an IP can bring the signal level below the scanner saturation threshold. This process, in turn, raises concerns about the signal response of IPs after an arbitrary number of scans and whether such a process yields, for example, a constant ratio of signal between the nth and n + 1st scan. Here, the sensitivity of IPs is investigated when scanned multiple times. It is demonstrated that the ratio of signal decay is not a constant with the number of scans and that the signal decay depends on the x-ray energy. As such, repeatedly scanning an IP with a mixture of signal types (e.g., x ray, neutron, and protons) enables ICF and HEDP diagnostics employing IPs to better isolate a particular signal type.

Image plate multi-scan response to fusion protons in the range of 1-14 MeV.

Image plates (IPs) are a quickly recoverable and reusable radiation detector often used to measure proton and x-ray fluence in laser-driven experiments. Recently, IPs have been used in a proton radiography detector stack on the OMEGA laser, a diagnostic historically implemented with CR-39, or radiochromic film. The IPs used in this and other diagnostics detect charged particles, neutrons, and x-rays indiscriminately. IPs detect radiation using a photo-stimulated luminescence (PSL) material, often phosphor, in which electrons are excited to metastable states by ionizing radiation. Protons at MeV energies deposit energy deeper into the IP compared with x rays below ∼20 keV due to the Bragg peak present for protons. This property is exploited to discriminate between radiation types. Doses of mono-energetic protons between 1.7 and 14 MeV are applied to IPs using the MIT linear electrostatic ion accelerator. This paper presents the results from consecutive scans of IPs irradiated with different proton energies. The PSL ratios between subsequent scans are shown to depend on proton energy, with higher energy protons having lower PSL ratios for each scan. This finding is separate from the known energy dependence in the absolute sensitivity of IPs. The results can be compared to complimentary work on x rays, showing a difference between protons and x rays, forging a path to discriminate between proton and x-ray fluence in mixed radiation environments.

Characterization of the response of radiochromic film to quasi-monoenergetic x rays through a cross-calibration with image plates.

Radiochromic film (RCF) and image plates (IPs) are both commonly used detectors in diagnostics fielded at inertial confinement fusion (ICF) and high-energy-density physics (HEDP) research facilities. Due to the intense x-ray background in all ICF/HEDP experiments, accurately calibrating the optical density of RCF as a function of x-ray dose, and the photostimulated luminescence per photon of IPs as a function of x-ray energy, is necessary for interpreting experimental results. Various measurements of the sensitivity curve of different IPs to x rays have been performed [Izumi et al., Proc. SPIE 8850, 885006 (2013) and Rosenberg et al., Rev. Sci. Instrum. 90(1), 013506 (2019)]; however, calibrating RCF is a tedious process that depends on factors such as the orientation in which the RCF is scanned in the film scanner and the batch of RCF used. These issues can be mitigated by cross-calibrating RCF with IPs to enable the use of IPs for the determination of dose on the RCF without scanning the RCF. Here, the first cross-calibration of RCF with IPs to quasi-monoenergetic titanium, copper, and molybdenum K-line x rays is presented. It is found that the IP-inferred dose rates on the RCF for the Ti and Mo x rays agree well with the measured dose rates, while the IP-inferred dose rate for the Cu x rays is larger than the measured dose rate by ∼2×. Explanations for this discrepancy and plans for future work are discussed.

Learning from each other: Cross-cutting diagnostic development activities between magnetic and inertial confinement fusion (invited).

Inertial Confinement Fusion and Magnetic Confinement Fusion (ICF and MCF) follow different paths toward goals that are largely common. In this paper, the claim is made that progress can be accelerated by learning from each other across the two fields. Examples of successful cross-community knowledge transfer are presented that highlight the gains from working together, specifically in the areas of high-resolution x-ray imaging spectroscopy and neutron spectrometry. Opportunities for near- and mid-term collaboration are identified, including in chemical vapor deposition diamond detector technology, using gamma rays to monitor fusion gain, handling neutron-induced backgrounds, developing radiation hard technology, and collecting fundamental supporting data needed for diagnostic analysis. Fusion research is rapidly moving into the igniting and burning regimes, posing new opportunities and challenges for ICF and MCF diagnostics. This includes new physics to probe, such as alpha heating; increasingly harsher environmental conditions; and (in the slightly longer term) the need for new plant monitoring diagnostics. Substantial overlap is expected in all of these emerging areas, where joint development across the two subfields as well as between public and private researchers can be expected to speed up advancement for all.

Hormone treatment without surgery for patients aged 75 years or older with operable breast cancer.

PURPOSE: To evaluate the trend in the use of primary endocrine treatment (PET) for elderly patients with operable breast cancer and to study mean time to response (TTR), local control, time to progression (TTP), and overall survival. METHODS: Data of 184 patients aged≥75 years, diagnosed with breast cancer in the south of the Netherlands between 2001 and 2008 and receiving PET, were analyzed. RESULTS: The percentage of women≥75 years with breast cancer receiving PET in the south of the Netherlands decreased from 23% in the period 1988-1992 to 12% in 1997-2000, and increased to 29% in 2005-2008. Mean age at diagnosis of 184 patients treated with PET in the period 2001-2008 was 84 years (range 75-89 years). Mean length of follow-up was 2.6 years. In 107 patients (58%), an initial response was achieved (mean TTR 7 months), 21 patients (12%) showed stable disease. A total of 64 patients (35%), with or without prior response, eventually displayed progression (mean TTP 20 months). No differences in TTR and TTP were observed between the patients starting with tamoxifen or an aromatase inhibitor. One hundred nineteen (65%) of 184 patients had died by January 1, 2010. In 17 patients (14%), breast cancer was the cause of death. CONCLUSIONS: Tumor progression was observed in a substantial proportion of the cohort, but only a small number of patients died of breast cancer. Further research is needed on the safety and effectiveness of PET for elderly women with breast cancer to justify the current widespread use.

Implementation of the foil-on-hohlraum technique for the magnetic recoil spectrometer for time-resolved neutron measurements at the National Ignition Facility.

The next-generation Magnetic Recoil Spectrometer, called MRSt, will provide time-resolved measurements of the deuterium-tritium-neutron spectrum from inertial confinement fusion implosions at the National Ignition Facility. These measurements will provide critical information about the time evolution of the fuel assembly, hot-spot formation, and nuclear burn. The absolute neutron spectrum in the energy range of 12-16 MeV will be measured with high accuracy (∼5%), unprecedented energy resolution (∼100 keV) and, for the first time ever, time resolution (∼20 ps). Crucial to the design of the system is a CD conversion foil for the production of recoil deuterons positioned as close to the implosion as possible. The foil-on-hohlraum technique has been demonstrated by placing a 1-mm-diameter, 40-µm-thick CD foil on the hohlraum diagnostic band along the line-of-sight of the current time-integrated MRS system, which measured the recoil deuterons. In addition to providing validation of the foil-on-hohlraum technique for the MRSt design, substantial improvement of the MRS energy resolution has been demonstrated.

A stretch/compress scheme for a high temporal resolution detector for the magnetic recoil spectrometer time (MRSt).

A time-resolved detector concept for the magnetic recoil spectrometer for time-resolved measurements of the NIF neutron spectrum is presented. The measurement is challenging due to the time spreading of the recoil protons (or deuterons) as they transit an energy dispersing magnet system. Ions arrive at the focal plane of the magnetic spectrometer over an interval of tens of nanoseconds. We seek to measure the time-resolved neutron spectrum with 20 ps precision by manipulating an electron signal derived from the ions. A stretch-compress scheme is employed to remove transit time skewing while simultaneously reducing the bandwidth requirements for signal recording. Simulation results are presented along with design concepts for structures capable of establishing the required electromagnetic fields.

The magnetic recoil spectrometer (MRSt) for time-resolved measurements of the neutron spectrum at the National Ignition Facility (NIF).

The next-generation magnetic recoil spectrometer for time-resolved measurements of the neutron spectrum has been conceptually designed for the National Ignition Facility. This spectrometer, called MRSt, represents a paradigm shift in our thinking about neutron spectrometry for inertial confinement fusion applications, as it will provide simultaneously information about the burn history and time evolution of areal density (ρR), apparent ion temperature (Ti), yield (Yn), and macroscopic flows during burn. From this type of data, an assessment of the evolution of the fuel assembly, hotspot, and alpha heating can be made. According to simulations, the MRSt will provide accurate data with a time resolution of ∼20 ps and energy resolution of ∼100 keV for total neutron yields above ∼1016. At lower yields, the diagnostic will be operated at a higher-efficiency, lower-energy-resolution mode to provide a time resolution of ∼20 ps.

Signal and background considerations for the MRSt on the National Ignition Facility (NIF).

A Magnetic Recoil Spectrometer (MRSt) has been conceptually designed for time-resolved measurements of the neutron spectrum at the National Ignition Facility. Using the MRSt, the goals are to measure the time-evolution of the spectrum with a time resolution of ∼20-ps and absolute accuracy better than 5%. To meet these goals, a detailed understanding and optimization of the signal and background characteristics are required. Through ion-optics, MCNP simulations, and detector-response calculations, it is demonstrated that the goals and a signal-to background >5-10 for the down-scattered neutron measurement are met if the background, consisting of ambient neutrons and gammas, at the MRSt is reduced 50-100 times.

Oxidizing intermediates generated in the Fenton reagent: kinetic arguments against the intermediacy of the hydroxyl radical.

It has long been recognized that the aqueous mixture of hydrogen peroxide and ferrous ion, known as the Fenton reagent, generates powerful oxidants. Furthermore, the chemical intermediates and reaction pathways of the type generated by this reagent have been implicated in oxidative damage in biological systems. Although the subject continues to be debated, the hydroxyl radical (.OH) is generally invoked as the predominant oxidizing intermediate formed by the Fenton reagent. However, recent results from this laboratory have demonstrated that the principal pathway for the Fenton-mediated oxidation of N-nitrosodimethylamine does not involve .OH, but instead must involve the intermediacy of another strongly oxidizing species. This conclusion was based on stopped-flow spectrophotometric observation of a transient, A, believed to be an iron(II) nitrosyl adduct, which was formed at a rate five-fold faster than that predicted for formation of .OH. Subsequent experiments have shown that methanol and other organic compounds can quench the formation of A. This quenching procedure provides a unique spectrophotometric probe with which to examine the relative reactivities of putative Fenton-type oxidizing intermediates toward organic substrates. Presented here are the results of several such quenching studies, plus an overview of our mechanistic investigations of the Fenton reaction.

Alteration of femoral structure in later life by chronically feeding caffeine during rapid growing period in newborn female rats.

The effects of caffeine intake in early life on bone structure later in life were studied in rats. At day 9 of gestation, dams were divided into 2 groups. Group 1 (control) received a 20% protein diet; group 2 received the 20% protein diet supplemented with caffeine (2 mg/100 g body weight). After birth pups were continuously fed their respective diets until day 93, when the diet of group 2 was replaced with a noncaffeine 20% protein diet. On day 388 animals from both groups were weighed, killed, and femora and mandibles were removed. Calcium, phosphorus, magnesium, zinc, hydroxyproline, and hexosamine concentrations were measured. Radiographs of some femora were taken and paraffin cross sections were made at the midshaft of others. Femora in the caffeine group were wider, periosteal bone area/total bone area was greater, the cross sectional area of femoral bone was smaller, and there were fewer osteocytes/bone area than in controls. Calcium, phosphorus, zinc, and hydroxyproline concentrations in the caffeine group were less in both bones of the caffeine group. These results indicate that if animals are exposed to caffeine during the rapidly growing period, changes occur in femoral bone which are similar to those that occur with aging.

Response of adult murine uterine epithelium to 50% methoxychlor.

This study was designed to assess the response of uterine epithelia of adult mice to a 4-week exposure of 50% methoxychlor (MXC) to ascertain whether significant changes were induced by 50% MXC that might compromise future implantation. Sexually mature virgin female mice were exposed to 0.1, 0.5, 1.0, 2.5, or 5.0 mg MXC via oral gavage for 5 consecutive days for 4 weeks. Controls received either sesame oil or 25 micrograms estradiol-17 beta (E-17 beta) also by gavage. At sacrifice, segments from each uterine horn were prepared for morphometric studies or for transmission electron microscopy. Results revealed a dose-dependent increase in the heights of uterine epithelial cells. Epithelial cell heights of the two groups treated with the highest doses of the pesticide were similar to that of the E-17 beta-treated group. Electron microscopy revealed increased vacuolization and swelling of mitochondria in cells of the 2.5 and 5.0 mg treated groups when compared to either of the control groups. In addition, there were effects on the number and size of microvilli in the uterine epithelial cells. The present study clearly demonstrates that a 4-week exposure of adult female mice to 50% MXC elicits significant estrogenic and toxic effects on the uterine epithelium.

Neural elements in human cervical intervertebral discs.

This study attempted to characterize neural elements within the human cervical intervertebral disc. Cervical intervertebral discs were obtained from four adult human subjects at autopsy. Discs were stained in bulk with gold chloride, sectioned, and viewed with the light microscope. Nerve fibers appeared to enter the disc in the posterolateral direction and course both parallel and perpendicular to the bundles of the anulus fibrosus. Nerves were seen throughout the anulus but were most numerous in the middle third of the disc. Receptors resembling Pacinian corpuscles and Golgi tendon organs were seen in the posterolateral region of the upper third of the disc. These results provide further evidence that human cervical intervertebral discs are supplied with both nerve fibers and mechanoreceptors.

Evidence of reinnervation of free patellar tendon autograft used for anterior cruciate ligament reconstruction.

We studied six adult male dogs to determine whether free patellar tendon grafts show evidence of reinnervation when used for anterior cruciate ligament reconstruction. Histologic return of neural elements and return of a somatosensory-evoked potential defined evidence of reinnervation. Before removal, the native anterior cruciate ligament was electrically stimulated with a bipolar electrode and a somatosensory-evoked potential was recorded from a scalp electrode. The ligament was excised and reconstructed using an autogenous patellar tendon graft. Somatosensory-evoked potential was attempted immediately after reconstruction. Histology for nerve endings was performed on the native ligaments. Each animal underwent repeat arthrotomy 6 months later. The grafts were isolated and somatosensory-evoked potentials were attempted. An evoked potential was seen in all six dogs before reconstruction. No graft demonstrated a somatosensory-evoked potential acutely; however, 6 months postoperatively, the somatosensory-evoked potential returned in two cases. Histology of native ligaments showed that 25% of the 100 sections evaluated contained neural elements. Of the receptors present, 89% were mechanoreceptors and 11% were free nerve endings. Histologic examination of the graft tissue 6 months postoperatively revealed that all six grafts also contained neural elements. Mechanoreceptors and free nerve endings were present in approximately equal numbers in the grafts. The results of histology and somatosensory-evoked potential demonstrate that in at least some cases, free patellar tendon grafts show evidence of reinnervation when used for anterior cruciate ligament reconstruction.

Mechanoreceptors in the palmar wrist ligaments.

Three palmar wrist ligaments from fresh human cadavers were dissected from the proximal to the distal insertions and stained to identify the mechanoreceptors. Golgi organs, Pacinian corpuscles, Ruffini endings and free nerve endings were present in all three ligaments. In the radial collateral and radiolunate ligaments they were found in increased density towards the proximal and distal insertions. A more uniform distribution was found in the radioscaphocapitate ligament which has attachments to three bones. The palmar wrist ligaments may have a significant sensory role in maintaining the stability of the wrist and in controlling its movement. Although technically difficult, the surgical repair of traumatic wrist defects should attempt to preserve the innervation of the ligaments, shown to be mainly near bony attachments. This may allow improvement in postoperative outcomes by preserving some proprioception. In some painful post-traumatic or degenerative conditions, however, denervation may be advantageous.

Neuroreceptors in the tissues of the knee joint.

Four types of receptors have been described in the articular tissues of the knee joint in humans and animals. The first three types are encapsulated; the fourth is unencapsulated: type I, Ruffini endings; type II, Pacinian corpuscles; type III, Golgi tendon organs; and type IV, free nerve endings. Ruffini endings, Pacinian corpuscles, and free nerve endings are most prevalent in the fibrous joint capsule; Golgi tendon organs are most common in the collateral and cruciate ligaments and the menisci. In the anterior and posterior cruciate ligaments (ACL, PCL), receptors are concentrated at the tibial and femoral attachments of the ligaments. In the menisci, neural elements penetrate the horns and the outer and middle thirds of the body. Ruffini mechanoreceptors are believed to contribute mainly to maintenance of muscle tone, Pacinian corpuscles and Golgi tendon organs are stimulated during movement, and free nerve endings are nociceptors. Thus, receptors of the knee joint are able to produce a discriminating afferent inflow to the central nervous system (CNS), thereby contributing to the protection and function of the joint through the musculature.

Periarticular neural elements in the shoulder joint.

Due to its unconstrained nature, the glenohumeral joint must necessarily have several mechanisms to regulate its position in space. The neural mechanisms associated with this positioning have not been fully evaluated anatomically. In this study, three fresh-frozen human cadaveric adult shoulders were dissected. Specimens were excised from the proximal biceps insertion, the superior, middle, and inferior glenohumeral ligaments, and the capsule superior to the glenohumeral ligaments. In two specimens, a portion of glenoid labrum was analyzed using a modified gold chloride staining method and light microscopy. A portion of mid-biceps tendon was used as a control. In the superior glenohumeral ligament, 45% of sections contained neural elements consisting of Golgi's, Ruffini's, and Pacini's corpuscles as well as free nerve endings. The predominant types were Ruffini's and Golgi's. The middle glenohumeral ligament sections revealed all four receptor types in 42%, with the most common elements being Pacini's and Ruffini's receptors. The inferior glenohumeral ligament specimens contained the four receptor types in 48% of sections, with Ruffini's, Pacini's, and Golgi's types equally distributed. The shoulder capsule specimens revealed Ruffini's and Pacini's receptors in 47.5% of sections. Only free nerve endings were identified in the biceps tendon and glenoid labral tissue. These findings suggest that the pattern of neural elements does not appear to be random in nature and may have some correlation with the specific functions of some of the glenohumeral ligaments.

Effects of a Novel Dental Gel on Plaque and Gingivitis: A Comparative Study.

OBJECTIVES: The goal of this prospective, randomized, controlled, double-blinded study was to evaluate the effects of a novel dental gel on plaque and gingival health. The dental gel was designed to (1) break up and prevent re-accumulation of microbial biofilm, and (2) inhibit metal mediated inflammation. MATERIALS AND METHODS: Twenty-five subjects with moderate gingival inflammation (Löe and Silness Gingival Index ≥2) and pocket depths <4 were randomly assigned to brush twice daily for 21 days with the test or the control dental gel. On Days 0, 7, 14 and 21, plaque levels (Quigley-Hein, Turesky Modification Plaque Index), gingival inflammation (Löe and Silness Gingival Index) and gingival bleeding (modified Sulcus Bleeding Index) were determined by one blinded, investigator using a pressure sensitive probe. RESULTS: After 3 weeks, all 3 clinical indices were significantly improved in both groups (P<0.05) and significantly lower in the test group (P<0.05). CONCLUSION: The novel dental gel formulation was provided effective plaque control and reduced gingival inflammation. CLINICAL RELEVANCE: A novel dentifrice formulation may be an effective tool for plaque removal and maintaining gingival health.