Comparison of Negative Pressure Wound Therapy with or without a Split-Thickness Skin Graft in the Surgical Management of Axillary Hidradenitis Suppurativa: A Retrospective Cohort Study.

Introduction: Negative pressure wound therapy (NPWT) alone or with the addition of a split-thickness skin graft (STSG) are 2 reconstructive options available after surgical excision of axillary hidradenitis suppurativa (HS). The aim of this study was to retrospectively examine patients undergoing these treatments and to assess clinical and patient-related outcome measures. Methods: A single-centre, retrospective analysis was conducted, evaluating surgical excision of axillary HS, with STSG and NPWT, or NPWT alone. Data collected included No. of post-operative clinic visits, time to heal, size of wound, disease recurrence, follow-up time, Dermatology Life Quality Index (DLQI), the Generalised Anxiety Disorder Assessment (GAD-7), the Patient Health Questionnaire Depression Scale (PHQ-9), Pain Visual Analogue Scale (PAINVAS2), the Brief Illness Perception Questionnaire (BIPQ), and Dermatology Visual Analogue Scale (DERMVAS). Two-tailed t-test and Mann-Whitney Wilcoxon U-tests were used to assess for significant relationships. Results: One hundred five patients were included in the study, 44 who received NPWT alone, and 61 who received NPWT + STSG. There was no significant difference in follow-up time (P = .934) or No. of follow-up appointments between groups (P = .287). There was a significant difference in time to heal between groups, with STSG + NPWT observing a mean time of 2.77 months and NPWT alone observing a mean time of 4.40 months (P = .0006). There was no difference in patient-reported outcomes between the 2 groups. Conclusion: There is no difference in patient-reported outcomes with the addition of an STSG to NPWT after surgical excision of HS. Wide excision and use of NPWT alone is an effective procedure for the treatment of axillary HS.

Introduction: Le traitement des plaies par pression négative (NPWT) seule ou associée à une greffe de peau d'épaisseur partielle (STSG) sont les deux options disponibles pour la reconstruction après excision chirurgicale d'hidradénite suppurée (HS) axillaire. Le but de cette étude rétrospective était d'examiner les patients subissant ces traitements et d'évaluer les mesures des résultats cliniques et liés aux patients. Méthodes: Une analyse rétrospective monocentrique a été menée pour évaluer l'excision chirurgicale de l'HS axillaire avec NPWT et STSG ou NPWT seule. La collecte de données a inclus : le nombre de visites cliniques postopératoires, le délai de guérison, la taille de la plaie, la récidive de la maladie, la durée du suivi, l'indice de qualité de vie dermatologique (DLQI), l'évaluation du trouble anxieux généralisé (GAD-7), l'échelle de dépression du Questionnaire sur la santé du patient (PHQ-9), l'échelle visuelle analogique de la douleur (PAINVAS2), le Court Questionnaire sur la perception de la maladie (BIPQ) et la DERMVAS. Un test t de Fisher bilatéral et un test de Mann-Whitney Wilcox ont servi à évaluer les relations significatives. Résultats: 105 patients ont été inclus dans l'étude : 44 ont reçu uniquement le traitement par pression négative et 61 ont reçu NPWT + STSG. Il n'y a pas eu de différence significative dans la durée du suivi (P = 0934) ou le nombre de rendez-vous de suivi entre les groupes (P = 0287). Il y a eu une différence significative sur le délai de guérison entre les groupes avec un délai moyen de 2,77 mois pour le groupe STSG + NPWT et de 4,40 mois pour le groupe NPWT seul (P = 0,0006). Il n'y a pas eu de différence entre les deux groupes pour ce qui concernait les résultats signalés par les patients. Conclusion: L'ajout d'une greffe de peau d'épaisseur partielle (STSG) au traitement par pression négative (NPWT) n'a pas entraîné d'augmentation de problèmes signalés par les patients après excision chirurgicale d'une hidradénite suppurée. Une excision large et l'utilisation du NPWT seul constituent une procédure efficace pour le traitement de l'HS axillaire.

Tinkering with care: Implementing extended-release buprenorphine depot treatment for opioid dependence.

We examine how extended-release buprenorphine depot (BUP-XR) is put to use and made to work in implementation practices, attending to how care practices are challenged and adapted as a long-acting technology is introduced into service in opioid agonist treatment (OAT) in Australia. Our approach is informed by ideas in science and technology studies (STS) emphasising the irreducible entanglement of care practices and technology, and in particular the concept of 'tinkering' as a practice of adaptation. To make our analysis, we draw on qualitative interview accounts (n = 19) of service providers involved in BUP-XR implementation across five sites. Our analysis considers the disruptive novelty of BUP-XR. Tinkering to make a novel technology work in practice slows down the expectation of implementation in relation to transformative innovation, despite the promise of dramatic or rapid change. Tinkering allowed for more open relations, for new care practices that departed from the routine and familiar, opening potential for how BUP-XR could be put to use and made to work in its new situation, and as its situation evolved along-with its implementation. Flexibility and openness of altering relations was, however, at times, held in tension with inflexibility and closure. This analysis identifies a concern for what is made present and what is made absent in the altered care network affected by BUP-XR, with the multiple effects of supervised daily dosing practices thrown into relief as they become absented. Tinkering to implement BUP-XR locally connects with a broader assemblage of trial and movement in the constitution of treatment. The introduction of long-acting technologies prompts new questions about embedded implementation practices, including supervised dosing, urinalysis, the time and place of psychosocial support, and how other social aspects of care might be recalibrated in drug treatment.

Alcohol use as a mediator of the effect of two alcohol reduction interventions on mental health symptoms of ART clients in Vietnam.

We aimed to examine the mediating role of alcohol use in the pathway from the interventions to depression and anxiety symptoms using data from a randomized controlled trial among people living with HIV (PWH) with hazardous alcohol use (n = 440) in Thai Nguyen, Vietnam. Participants were randomized into either a combined intervention (CoI), a brief intervention (BI) and a standard of care arm. Both interventions were based on cognitive behavioral therapy and motivational enhancement therapy. Alcohol use was measured as the percentage of days abstinent from alcohol in the last 30 days. Symptoms of depression and anxiety were measured with the Patient Health Questionnaire-9 and Generalized Anxiety Disorder-7 scales. Alcohol use was a significant mediator of the effects of two alcohol interventions on depression symptoms, but not anxiety symptoms. There were significant indirect effects via alcohol use of both interventions on depression symptoms at 12 months (CoI: mean difference (MD) = -0.134; 95%CI: -0.251, -0.035); (BI: MD = -0.141; 95%CI: -0.261, -0.038). There were no significant direct or total effects of the interventions on either symptoms at 12 months. Interventions with a dual focus on mental health and alcohol disorders are needed to determine optimal ways to tackle these common comorbidities among PWH.

"I refused to drink but they still forced me": A mixed-methods approach to understanding the pathways to reduce alcohol use among Vietnamese people with HIV.

AIMS: This study explores the effects of two evidence-based alcohol reduction counseling interventions on readiness to change, alcohol abstinence self-efficacy, social support, and alcohol abstinence stigma among people with HIV (PWH) who have hazardous alcohol use in Vietnam. METHODS: PWH receiving antiretroviral therapy (ART) were screened for hazardous drinking and randomized to one of three study arms: combined intervention (CoI), brief intervention (BI), and standard of care (SOC). A quantitative survey was conducted at baseline (N = 440) and 3-month post-intervention (N = 405), while in-depth interviews were conducted with a subset of BI and CoI participants at baseline (N = 14) and 3 months (N = 14). Data was collected from March 2016 to August 2017. A concurrent mixed-methods model was used to triangulate quantitative and qualitative data to cross-validate findings. RESULTS: At 3 months, receiving the BI and CoI arms was associated with 2.64 and 3.50 points higher in mean readiness to change scores, respectively, compared to the SOC group (BI: ß = 2.64, 95% CI: 1.17-4.12; CoI: ß = 3.50, 95% CI 2.02-4.98). Mean alcohol abstinence self-efficacy scores were 4.03 and 3.93 points higher among the BI and CoI arm at 3 months, compared to SOC (BI: ß = 4.03, 95% CI: 0.17-7.89; CoI: ß = 3.93, 95% CI: 0.05-7.81). The impacts of the interventions on social support and alcohol abstinence stigma were not significant. Perceived challenges to refusing drinks at social events remained due to strong alcohol abstinence stigma and perceived negative support from family and friends who encouraged participants to drink posed additional barriers to reducing alcohol use. CONCLUSIONS: Both the CoI and BI were effective in improving readiness to change and alcohol abstinence self-efficacy among PWH. Yet, participants still faced significant barriers to reducing their drinking due to social influences and pressure to drink. Interventions at different levels addressing social support and alcohol abstinence stigma are warranted.

Effects of Two Alcohol Reduction Interventions on Depression and Anxiety Symptoms of ART Clients in Vietnam.

Little is known about the potential mental health impacts of cognitive behavioral therapy and motivational interviewing interventions that focus on alcohol reduction among people with HIV (PWH). Our study aimed to assess the impact of two evidence-based alcohol reduction interventions on depression and anxiety symptoms of antiretroviral therapy (ART) clients with hazardous alcohol use. We conducted a secondary data analysis of data from a three-arm randomized controlled trial among ART clients in Thai Nguyen, Vietnam that evaluated the impacts of two alcohol reduction interventions in Vietnam. ART clients 18 years old or more with hazardous alcohol use (based on the Alcohol Use Disorders Identification Test-Consumption) were enrolled and randomized into one of three arms: Combined intervention, Brief intervention, and Standard of care (SOC). Symptoms of depression, measured with the Patient Health Questionnaire-9, and anxiety, measured with the Generalized Anxiety Disorder-7 scale, were assessed at baseline and 3, 6, and 12 months post-intervention. Generalized estimating equations were used to evaluate the effects of the interventions on depression and anxiety symptoms. The prevalence of depression and anxiety symptoms at baseline was 25.1% and 16.1%, respectively. Decreases in depression and anxiety symptoms were observed in all three arms from baseline to 12-month follow-up. There were no significant differences in depression and anxiety symptoms among participants receiving either intervention, relative to the SOC. Interventions with a dual focus on alcohol and mental health are needed to achieve more pronounced and sustainable improvements in depression and anxiety symptoms for PWH with hazardous alcohol use.

Role of relativistic laser intensity on isochoric heating of metal wire targets.

In a recent experimental campaign, we used laser-accelerated relativistic hot electrons to ensure heating of thin titanium wire targets up to a warm dense matter (WDM) state [EPL114, 45002 (2016)10.1209/0295-5075/114/45002]. The WDM temperature profiles along several hundred microns of the wire were inferred by using spatially resolved X-ray emission spectroscopy looking at the Ti Kα characteristic lines. A maximum temperature of ∼30 eV was reached. Our study extends this work by discussing the influence of the laser parameters on temperature profiles and the optimisation of WDM wire-based generation. The depth of wire heating may reach several hundreds of microns and it is proven to be strictly dependent on the laser intensity. At the same time, it is quantitatively demonstrated that the maximum WDM temperature doesn't appear to be sensitive to the laser intensity and mainly depends on the deposited laser energy considering ranges of 6×1018-6×1020 W/cm2 and 50-200 J.

Prospects for high gain inertial fusion energy: an introduction to the first special edition.

A European consortium of 15 laboratories across nine nations have worked together under the EUROFusion Enabling Research grants for the past decade with three principle objectives. These are: (a) investigating obstacles to ignition on megaJoule-class laser facilities; (b) investigating novel alternative approaches to ignition, including basic studies for fast ignition (both electron and ion-driven), auxiliary heating, shock ignition etc.; and (c) developing technologies that will be required in the future for a fusion reactor. The Hooke discussion meeting in March 2020 provided an opportunity to reflect on the progress made in inertial confinement fusion research world-wide to date. This first edition of two special issues seeks to identify paths forward to achieve high fusion energy gain. This article is part of a discussion meeting issue 'Prospects for high gain inertial fusion energy (part 1)'.

Social support modifies the association between hazardous drinking and depression symptoms among ART clients in Vietnam.

INTRODUCTION: Hazardous drinking is widespread among people with HIV (PWH). PWH are also vulnerable to depression due to HIV-related social stigma, and social support can play an important role in improving mental health for this population. No studies have explored whether social support modifies the association of hazardous drinking and depressive symptoms among PWH. METHODS: We used baseline data from a randomized controlled trial of two evidence-based alcohol reduction interventions among antiretroviral therapy clients in Vietnam. Hazardous alcohol use was defined as having a score ≥8 for men and ≥ 7 for women on the Alcohol Use Disorders Identification Test. The presence of depression symptoms was defined as a score ≥ 5 on the Patient Health Questionnaire-9. Social support was measured with a 5-question modified version of the Medical Outcomes Study Social Support Instrument. Crude (CPRs) and adjusted prevalence ratios (aPRs) of the association were presented. RESULTS: Hazardous drinking was significantly associated with increased likelihood of having depressive symptoms (aPR = 1.26;95%CI 1.04-1.52). Hazardous drinking and depression symptoms were not associated among those with high social support (aPR = 1.01;95%CI 0.76-1.35), but were associated among those with medium (aPR = 1.24;95%CI 0.92-1.69) and low social support (aPR = 1.71;95%CI 1.25-2.34). CONCLUSIONS: Social support significantly modified the association between hazardous drinking and depression symptoms among ART clients in Vietnam. Interventions to decrease hazardous alcohol use are broadly indicated for PWH in Vietnam and other low-resource settings, but special attention or modifications may be needed to support mental health among those with lower levels of social support.

Effect of plastic coating on the density of plasma formed in Si foil targets irradiated by ultra-high-contrast relativistic laser pulses.

The formation of high energy density matter occurs in inertial confinement fusion, astrophysical, and geophysical systems. In this context, it is important to couple as much energy as possible into a target while maintaining high density. A recent experimental campaign, using buried layer (or "sandwich" type) targets and the ultrahigh laser contrast Vulcan petawatt laser facility, resulted in 500 Mbar pressures in solid density plasmas (which corresponds to about 4.6×10^{7}J/cm^{3} energy density). The densities and temperatures of the generated plasma were measured based on the analysis of x-ray spectral line profiles and relative intensities.

An optically multiplexed single-shot time-resolved probe of laser-plasma dynamics.

We introduce a new approach to temporally resolve ultrafast micron-scale processes via the use of a multi-channel optical probe. We demonstrate that this technique enables highly precise time-resolved, two-dimensional spatial imaging of intense laser pulse propagation dynamics, plasma formation and laser beam filamentation within a single pulse over four distinct time frames. The design, development and optimization of the optical probe system is presented, as are representative experimental results from the first implementation of the multi-channel probe with a high-power laser pulse interaction with a helium gas jet target.

Characteristics of persons who inject drugs and who witness opioid overdoses in Vietnam: a cross-sectional analysis to inform future overdose prevention programs.

BACKGROUND: Persons who use opioids have a high risk of overdose and associated mortality. In Vietnam, little is known about the characteristics of this population and the persons who are witness to those overdoses. One approach to combatting fatal overdose has been the use of peer interventions in which a friend or injecting partner administers overdose reversal medication, but availability in Vietnam of these medications is limited to pilot programs with aims to expand in the future (Le Minh and V.F. Go, Personal Communication, 2016). The primary objective of this paper is to explore the characteristics associated with witnessing three or more overdoses in a lifetime. METHODS: This cross-sectional analysis used baseline data from a four-arm randomized control trial conducted in Thai Nguyen, Vietnam, known as the Prevention for Positives project. One thousand six hundred seventy-three PWID were included in the analysis. We conducted bivariable and multivariable logistic regression to identify characteristics associated with witnessing three or more overdoses in a lifetime. Characteristics explored included education, employment, marital status, risky drug use behaviors, locations for accessing syringes, recent overdose, history of incarceration, drug treatment, and having slept outside in the past 3 months. RESULTS: Seventy-two percent (n = 1203) of participants had witnessed at least one overdose in their lifetime, and 46% had witnessed three or more overdoses (n = 765). In the multivariable model, having less than secondary education (AOR 0.70; 95% CI 0.57, 0.86), having slept outside in the past 3 months (AOR 1.77; 95% CI 1.31, 2.40), having a history of incarceration (AOR 1.33; 95% CI 1.07, 1.65), having a history of drug treatment (AOR 1.41; 95% CI 1.12, 1.77), experiencing a recent non-fatal overdose (AOR 3.84; 95% CI 2.36, 6.25), injecting drugs daily (AOR 1.79; 95% CI 1.45, 2.20), receptive needle sharing (AOR 1.30; 95% CI 1.04, 1.63), and number of years injecting (AOR 1.04; 95% CI 1.02, 1.07) were significantly associated with witnessing three or more overdoses. CONCLUSIONS: Targeted interventions are needed to train persons witnessing an overdose to administer overdose-reversal medication. This includes targeting persons prior to release from prisons, drug treatment centers, and those accessing syringe exchange programs. Additional research should assess the burden of witnessing an overdose as well as locations for medication distribution. Assessments of the training capacity and needs for implementing these programs among drug using peers in Vietnam are of the utmost importance.

Micron-scale mapping of megagauss magnetic fields using optical polarimetry to probe hot electron transport in petawatt-class laser-solid interactions.

The transport of hot, relativistic electrons produced by the interaction of an intense petawatt laser pulse with a solid has garnered interest due to its potential application in the development of innovative x-ray sources and ion-acceleration schemes. We report on spatially and temporally resolved measurements of megagauss magnetic fields at the rear of a 50-µm thick plastic target, irradiated by a multi-picosecond petawatt laser pulse at an incident intensity of ~1020 W/cm2. The pump-probe polarimetric measurements with micron-scale spatial resolution reveal the dynamics of the magnetic fields generated by the hot electron distribution at the target rear. An annular magnetic field profile was observed ~5 ps after the interaction, indicating a relatively smooth hot electron distribution at the rear-side of the plastic target. This is contrary to previous time-integrated measurements, which infer that such targets will produce highly structured hot electron transport. We measured large-scale filamentation of the hot electron distribution at the target rear only at later time-scales of ~10 ps, resulting in a commensurate large-scale filamentation of the magnetic field profile. Three-dimensional hybrid simulations corroborate our experimental observations and demonstrate a beam-like hot electron transport at initial time-scales that may be attributed to the local resistivity profile at the target rear.

The productive techniques and constitutive effects of 'evidence-based policy' and 'consumer participation' discourses in health policy processes.

For over twenty years there have been calls for greater 'consumer' participation in health decision-making. While it is recognised by governments and other stakeholders that 'consumer' participation is desirable, barriers to meaningful involvement nonetheless remain. It has been suggested that the reifying of 'evidence-based policy' may be limiting opportunities for participation, through the way this discourse legitimates particular voices to the exclusion of others. Others have suggested that assumptions underpinning the very notion of the 'affected community' or 'consumers' as fixed and bounded 'policy publics' need to be problematised. In this paper, drawing on interviews (n = 41) with individuals closely involved in Australian drug policy discussions, we critically interrogate the productive techniques and constitutive effects of 'evidence-based policy' and 'consumer participation' discourses in the context of drug policy processes. To inform our analysis, we draw on and combine a number of critical perspectives including Foucault's concept of subjugated knowledges, the work of feminist theorists, as well as recent work regarding conceptualisations of emergent policy publics. First, we explore how the subject position of 'consumer' might be seen as enacted in the material-discursive practices of 'evidence-based policy' and 'consumer participation' in drug policy processes. Secondly, we consider the centralising power-effects of the dominant 'evidence-based policy' paradigm, and how resistance may be thought about in this context. We suggest that such interrogation has potential to recast the call for 'consumer' participation in health policy decision-making and drug policy processes.

Plasma scale-length effects on electron energy spectra in high-irradiance laser plasmas.

An analysis of an electron spectrometer used to characterize fast electrons generated by ultraintense (10^{20}Wcm^{-2}) laser interaction with a preformed plasma of scale length measured by shadowgraphy is presented. The effects of fringing magnetic fields on the electron spectral measurements and the accuracy of density scale-length measurements are evaluated. 2D EPOCH PIC code simulations are found to be in agreement with measurements of the electron energy spectra showing that laser filamentation in plasma preformed by a prepulse is important with longer plasma scale lengths (>8 µm).

Obesity interventions in African American faith-based organizations: a systematic review.

African Americans, especially women, have higher obesity rates than the general US population. Because of the importance of faith to many African Americans, faith-based organizations (FBOs) may be effective venues for delivering health messages and promoting adoption of healthy behaviours. This article systematically reviews interventions targeting weight and related behaviours in faith settings. We searched literature published through July 2012 for interventions in FBOs targeting weight loss, diet and/or physical activity (PA) in African Americans. Of 27 relevant articles identified, 12 were randomized controlled trials; seven of these reported a statistically significant change in an outcome. Four of the five quasi-experimental and single-group design studies reported a statistically significant outcome. All 10 pilot studies reported improvement in at least one outcome, but most did not have a comparison group. Overall, 70% of interventions reported success in reducing weight, 60% reported increased fruit and vegetable intake and 38% reported increased PA. These results suggest that interventions in African American FBOs can successfully improve weight and related behaviours. However, not all of the findings about the success of certain approaches were as expected. This review identifies gaps in knowledge and recommends more rigorous studies be conducted to strengthen the comparative methodology and evidence.

Characterization of Giardia lamblia genotypes in dogs from Tucson, Arizona using SSU-rRNA and ß-giardin sequences.

The objective of this study was to determine if human genotypes of Giardia lamblia could be found in canine companion animals from urban and peri-urban environments in Tucson, Arizona. Canine fecal samples collected from the Humane Society of Southern Arizona between July 2006 and April 2009 were screened for G. lamblia infection using immunofluorescent microscopy and confirmed by polymerase chain reaction (PCR). Of the 672 samples screened, 196 were found positive by IFA and 185 of those positive were successfully amplified through PCR. Sequencing analysis showed samples were primarily of the C or D genotypes (n =154), or showing a mix of the C and D genotypes (n =10). One sample showed a mixed infection of a human genotype (A) and a dog-specific genotype (C). These data are consistent with previous studies showing dog specific genotypes to be dominant in environments where dog-to-dog transmission is likely to occur, and provides further evidence that multiple genes should be targeted for more accurate genotype characterization.

Measuring fast electron spectra and laser absorption in relativistic laser-solid interactions using differential bremsstrahlung photon detectors.

A photon detector suitable for the measurement of bremsstrahlung spectra generated in relativistically intense laser-solid interactions is described. The Monte Carlo techniques used to extract the fast electron spectrum and laser energy absorbed into forward-going fast electrons are detailed. A relativistically intense laser-solid experiment using frequency doubled laser light is used to demonstrate the effective operation of the detector. The experimental data were interpreted using the 3-spatial-dimension Monte Carlo code MCNPX [D. Pelowitz, MCNPX User's Manual Version 2.6.0, Los Alamos National Laboratory, 2008], and the fast electron temperature found to be 125 keV.

HPA-axis hormone modulation of stress response circuitry activity in women with remitted major depression.

Decades of clinical and basic research indicate significant links between altered hypothalamic-pituitary-adrenal (HPA)-axis hormone dynamics and major depressive disorder (MDD). Recent neuroimaging studies of MDD highlight abnormalities in stress response circuitry regions which play a role in the regulation of the HPA-axes. However, there is a dearth of research examining these systems in parallel, especially as related to potential trait characteristics. The current study addresses this gap by investigating neural responses to a mild visual stress challenge with real-time assessment of adrenal hormones in women with MDD in remission and controls. Fifteen women with recurrent MDD in remission (rMDD) and 15 healthy control women were scanned on a 3T Siemens MR scanner while viewing neutral and negative (stress-evoking) stimuli. Blood samples were obtained before, during, and after scanning for the measurement of HPA-axis hormone levels. Compared to controls, rMDD women demonstrated higher anxiety ratings, increased cortisol levels, and hyperactivation in the amygdala and hippocampus, p<0.05, family-wise error (FWE)-corrected in response to the stress challenge. Among rMDD women, amygdala activation was negatively related to cortisol changes and positively associated with the duration of remission. Findings presented here provide evidence for differential effects of altered HPA-axis hormone dynamics on hyperactivity in stress response circuitry regions elicited by a well-validated stress paradigm in women with recurrent MDD in remission.

Exotic dense-matter states pumped by a relativistic laser plasma in the radiation-dominated regime.

In high-spectral resolution experiments with the petawatt Vulcan laser, strong x-ray radiation of KK hollow atoms (atoms without n = 1 electrons) from thin Al foils was observed at pulse intensities of 3 × 10(20) W/cm(2). The observations of spectra from these exotic states of matter are supported by detailed kinetics calculations, and are consistent with a picture in which an intense polychromatic x-ray field, formed from Thomson scattering and bremsstrahlung in the electrostatic fields at the target surface, drives the KK hollow atom production. We estimate that this x-ray field has an intensity of >5 × 10(18) W/cm(2) and is in the 3 keV range.

Controlling fast-electron-beam divergence using two laser pulses.

This Letter describes the first experimental demonstration of the guiding of a relativistic electron beam in a solid target using two colinear, relativistically intense, picosecond laser pulses. The first pulse creates a magnetic field that guides the higher-current, fast-electron beam generated by the second pulse. The effects of intensity ratio, delay, total energy, and intrinsic prepulse are examined. Thermal and Kα imaging show reduced emission size, increased peak emission, and increased total emission at delays of 4-6 ps, an intensity ratio of 10∶1 (second:first) and a total energy of 186 J. In comparison to a single, high-contrast shot, the inferred fast-electron divergence is reduced by 2.7 times, while the fast-electron current density is increased by a factor of 1.8. The enhancements are reproduced with modeling and are shown to be due to the self-generation of magnetic fields. Such a scheme could be of considerable benefit to fast-ignition inertial fusion.