Proposal for complete characterization of attosecond pulses from relativistic plasmas.

In this study, we propose two full-optical-setup and single-shot measurable approaches for complete characterization of attosecond pulses from surface high harmonic generation (SHHG): SHHG-SPIDER (spectral phase interferometry for direct electric field reconstruction) and SHHG-SEA-SPIDER (spatially encoded arrangement for SPIDER). 1D- and 2D-EPOCH PIC (particle-in-cell) simulations were performed to generate the attosecond pulses from relativistic plasmas under different conditions. Pulse trains dominated by single isolated peak as well as complex pulse train structures are extensively discussed for both methods, which showed excellent accuracy in the complete reconstruction of the attosecond field with respect to the direct Fourier transformed result. Kirchhoff integral theorem has been used for the near-to-far-field transformation. This far-field propagation method allows us to relate these results to potential experimental implementations of the scheme. The impact of comprehensive experimental parameters for both apparatus, such as spectral shear, spatial shear, cross-angle, time delay, and intensity ratio between the two replicas has been investigated thoroughly. These methods are applicable to complete characterization for SHHG attosecond pulses driven by a few to hundreds of terawatts femtosecond laser systems.

First-Line Nivolumab Plus Low-Dose Ipilimumab for Microsatellite Instability-High/Mismatch Repair-Deficient Metastatic Colorectal Cancer: The Phase II CheckMate 142 Study.

PURPOSE: Nivolumab received US Food and Drug Administration approval as a single agent or in combination with ipilimumab in patients with microsatellite instability-high/mismatch repair-deficient (MSI-H/dMMR) metastatic colorectal cancer (mCRC) that progressed following treatment with a fluoropyrimidine, oxaliplatin, and irinotecan based on CheckMate 142. Presented are results of nivolumab plus low-dose ipilimumab in the first-line therapy cohort from the phase II CheckMate 142 study. PATIENTS AND METHODS: Patients with no prior treatment in the metastatic setting for MSI-H/dMMR CRC were treated with nivolumab every 2 weeks plus low-dose ipilimumab every 6 weeks until disease progression. The primary end point was objective response rate (investigator assessment; RECIST v1.1). RESULTS: Median age of treated patients was 66 years (N = 45). Median follow-up was 29.0 months. Objective response rate and disease control rate were 69% (95% CI, 53 to 82) and 84% (95% CI, 70.5 to 93.5), respectively, with 13% complete response rate. Median duration of response was not reached; 74% of responders had ongoing responses at data cutoff. Median progression-free survival and median overall survival were not reached with minimum follow-up of 24.2 months (24-month rates, 74% and 79%, respectively). Clinical benefit was observed regardless of baseline demographic and tumor characteristics, including BRAF or KRAS mutation status. In a post hoc analysis, of 14 patients who discontinued treatment and did not receive subsequent therapy, 10 remained progression-free. Patient-reported outcomes were stable over the treatment period. Grade 3-4 treatment-related adverse events occurred in 22% of patients; 13% discontinued because of any-grade treatment-related adverse events. CONCLUSION: Nivolumab plus low-dose ipilimumab demonstrated robust and durable clinical benefit and was well tolerated as a first-line treatment for MSI-H/dMMR mCRC. Based on these promising data, randomized studies are warranted.

Durable Clinical Benefit With Nivolumab Plus Ipilimumab in DNA Mismatch Repair-Deficient/Microsatellite Instability-High Metastatic Colorectal Cancer.

Purpose Nivolumab provides clinical benefit (objective response rate [ORR], 31%; 95% CI, 20.8 to 42.9; disease control rate, 69%; 12-month overall survival [OS], 73%) in previously treated patients with DNA mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) metastatic colorectal cancer (mCRC); nivolumab plus ipilimumab may improve these outcomes. Efficacy and safety results for the nivolumab plus ipilimumab cohort of CheckMate-142, the largest single-study report of an immunotherapy combination in dMMR/MSI-H mCRC, are reported. Patients and Methods Patients received nivolumab 3 mg/kg plus ipilimumab 1 mg/kg once every 3 weeks (four doses) followed by nivolumab 3 mg/kg once every 2 weeks. Primary end point was investigator-assessed ORR. Results Of 119 patients, 76% had received ≥ two prior systemic therapies. At median follow-up of 13.4 months, investigator-assessed ORR was 55% (95% CI, 45.2 to 63.8), and disease control rate for ≥ 12 weeks was 80%. Median duration of response was not reached; most responses (94%) were ongoing at data cutoff. Progression-free survival rates were 76% (9 months) and 71% (12 months); respective OS rates were 87% and 85%. Statistically significant and clinically meaningful improvements were observed in patient-reported outcomes, including functioning, symptoms, and quality of life. Grade 3 to 4 treatment-related adverse events (AEs) occurred in 32% of patients and were manageable. Patients (13%) who discontinued treatment because of study drug-related AEs had an ORR (63%) consistent with that of the overall population. Conclusion Nivolumab plus ipilimumab demonstrated high response rates, encouraging progression-free survival and OS at 12 months, manageable safety, and meaningful improvements in key patient-reported outcomes. Indirect comparisons suggest combination therapy provides improved efficacy relative to anti-programmed death-1 monotherapy and has a favorable benefit-risk profile. Nivolumab plus ipilimumab provides a promising new treatment option for patients with dMMR/MSI-H mCRC.

Long-term operation of surface high-harmonic generation from relativistic oscillating mirrors using a spooling tape.

Surface high-harmonic generation in the relativistic regime is demonstrated as a source of extreme ultra-violet (XUV) pulses with extended operation time. Relativistic high-harmonic generation is driven by a frequency-doubled high-power Ti:Sapphire laser focused to a peak intensity of 3·10(19) W/cm2 onto spooling tapes. We demonstrate continuous operation over up to one hour runtime at a repetition rate of 1 Hz. Harmonic spectra ranging from 20 eV to 70 eV (62 nm to 18 nm) were consecutively recorded by an XUV spectrometer. An average XUV pulse energy in the µJ range is measured. With the presented setup, relativistic surface high-harmonic generation becomes a powerful source of coherent XUV pulses that might enable applications in, e.g. attosecond laser physics and the seeding of free-electron lasers, when the laser issues causing 80-% pulse energy fluctuations are overcome.

Diagnostics for studies of novel laser ion acceleration mechanisms.

Diagnostic for investigating and distinguishing different laser ion acceleration mechanisms has been developed and successfully tested. An ion separation wide angle spectrometer can simultaneously investigate three important aspects of the laser plasma interaction: (1) acquire angularly resolved energy spectra for two ion species, (2) obtain ion energy spectra for multiple species, separated according to their charge to mass ratio, along selected axes, and (3) collect laser radiation reflected from and transmitted through the target and propagating in the same direction as the ion beam. Thus, the presented diagnostic constitutes a highly adaptable tool for accurately studying novel acceleration mechanisms in terms of their angular energy distribution, conversion efficiency, and plasma density evolution.