Proton acceleration by a relativistic laser frequency-chirp driven plasma snowplow

We analyze the use of a relativistic laser pulse with a controlled frequency chirp incident on a rising plasma density gradient to drive an acceleration structure for proton and light-ion acceleration. The Chirp Induced Transparency Acceleration (ChITA) scheme is described with an analytical model of the velocity of the snowplow at critical density on a pre-formed rising plasma density gradient that is driven by a positive-chirp in the frequency of a relativistic laser pulse. The velocity of the ChITA-snowplow is shown to depend upon rate of rise of the frequency of the relativistic laser pulse represented by $frac{epsilon_0}{theta}$ where, $epsilon_0 = frac{Deltaomega_0}{omega_0}$ and chirping spatial scale-length, $theta$, the normalized magnetic vector potential of the laser pulse $a_0$ and the plasma density gradient scale-length, $alpha$. We observe using 1-D OSIRIS simulations the formation and forward propagation of ChITA-snowplow, being continuously pushed by the chirping laser at a velocity in accordance with the analytical results. The trace protons reflect off of this propagating snowplow structure and accelerate mono-energetically. The control over ChITA-snowplow velocity allows the tuning of accelerated proton energies

Community- delivered infant- parent psychotherapy improves maternal sensitive caregiving: Evaluation of the Michigan model of infant mental health home visiting

The current study evaluated the effectiveness of a home- based psychotherapeutic Infant Mental Health Home Visiting (IMH- HV) intervention for enhancing parenting sensitivity; a secondary aim was to evaluate whether the use of video feedback was associated with greater treatment response. Participants were N = 78 mothers and their children (age at entry ranged from prebirth to 24- month old (M = 9.8, SD = 8.4), who were initiating IMH- HV services with community mental health- based therapists (N = 51). Dyads were assessed during extended home visits via standardized interviews and observational and questionnaire methods within the first month of treatment (baseline), and again 6 and 12 months thereafter. Following each of these extended home visits, study evaluators completed a standard Q- sort to capture observations of maternal sensitivity during the visit. Therapists completed fidelity checklists used to derive the total number of IMH- HV sessions received (i.e., dosage) and frequency with which therapists provided video feedback. Results indicated a dose- response relationship between number of sessions and maternal sensitivity, and that video review with parents independently contributed to improved maternal sensitivity. Discussion focuses on the effectiveness of this community- based psychotherapeutic home visiting model for enhancing parenting, as well as the value of video feedback as a specific therapeutic strategy.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154891/1/imhj21840_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154891/2/imhj21840.pd

Enabling Lorentz boosted frame particle-in-cell simulations of laser wakefield acceleration in quasi-3D geometry

When modeling laser wakefield acceleration (LWFA) using the particle-in-cell (PIC) algorithm in a Lorentz boosted frame, the plasma is drifting relativistically at beta(b)c towards the laser, which can lead to a computational speedup of similar to gamma(2)(b)=(1-beta(2)(b))-1. Meanwhile, when LWFA is modeled in the quasi-3D geometry in which the electromagnetic fields and current are decomposed into a limited number of azimuthal harmonics, speedups are achieved by modeling three dimensional (3D) problems with the computational loads on the order of two dimensional r-z simulations. Here, we describe a method to combine the speedups from the Lorentz boosted frame and quasi-3D algorithms. The key to the combination is the use of a hybrid Yee-FFT solver in the quasi-3D geometry that significantly mitigates the Numerical Cerenkov Instability (NCI) which inevitably arises in a Lorentz boosted frame due to the unphysical coupling of Langmuir modes and EM modes of the relativistically drifting plasma in these simulations. In addition, based on the space-time distribution of the LWFA data in the lab and boosted frame, we propose to use a moving window to follow the drifting plasma, instead of following the laser driver as is done in the LWFA lab frame simulations, in order to further reduce the computational loads. We describe the details of how the NCI is mitigated for the quasi-3D geometry, the setups for simulations which combine the Lorentz boosted frame, quasi-3D geometry, and the use of a moving window, and compare the results from these simulations against their corresponding lab frame cases. Good agreement is obtained among these sample simulations, particularly when there is no self-trapping, which demonstrates it is possible to combine the Lorentz boosted frame and the quasi-3D algorithms when modeling LWFA. We also discuss the preliminary speedups achieved in these sample simulations.info:eu-repo/semantics/submittedVersio