Intense terahertz pulses from SPARC-LAB coherent radiation source

The linac-based Terahertz source at the SPARC_LAB test facility is able to gene rate highly intense Terahertz broadband pulses via coherent transition radiation (CTR) from high brightness electron beams. The THz pulse duration is typically down to 100 fs RMS and can be tuned through the electron bunch duration and shaping. The measured stored energy in a single THz pulse has reached 40 μ J, which corresponds to a peak electric field of 1.6 MV/cm at the THz focus. Here we present the main features, in particular spatial and sp ectral distributions and energy characterizations of the SPARC_LAB THz source, which is very competitive for investigations in Condensed Matter, as well as a valid tool for electron beam longitudinal diagnostics

An Agent-Based Model to Support Infection Control Strategies at School

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Beam manipulation for resonant plasma wakefield acceleration

Plasma-based acceleration has already proved the ability to reach ultra-high accelerating gradients. However the step towards the realization of a plasma-based accelerator still requires some e ff ort to guarantee high brightness beams, stability and reliability. A significant improvement in the efficiency of PWFA has been demonstrated so far accelerating a witness bunch in the wake of a higher charge driver bunch. The transformer ratio, therefore the energy transfer from the driver to the witness beam, can be increased by resonantly exciting the plasma with a properly pre-shaped drive electron beam. Theoretical and experimental studies of beam manipulation for resonant PWFA will be presented her

Operational experience on the generation and control of high brightness electron bunch trains at SPARC-LAB

Sub-picosecond, high-brightness electron bunch trains are routinely produced at SPARC-LAB via the velocity bunching technique. Such bunch trains can be used to drive multi-color Free Electron Lasers (FELs) and plasma wake field accelerators. In this paper we present recent results at SPARC-LAB on the generation of such beams, highlighting the key points of our scheme. We will discuss also the on-going machine upgrades to allow driving FELs with plasma accelerated beams or with short electron pulses at an increased energy

Sentinel Lymph Node Biopsy in Malignant Melanoma of the Head and Neck: A Single Center Experience

Purpose: This study evaluated the characteristics of patients with head and neck (H&N) melanoma who underwent sentinel lymph node biopsy (SNLB) and assessed the clinical course of patients categorizing subjects according to SLNB status and melanoma location (scalp area vs. non-scalp areas). Methods: Patients undergoing SLNB for melanoma of H&N from 2015 to 2021 were prospectively characterized according to sentinel lymph node (SLN) status. SPECT/CT had been previously performed. Patients were followed until the first adverse event to evaluate progression-free survival. Results: 93 patients were enrolled. SLNB was negative in 75 patients. The median Breslow index was higher for patients with positive SLNB compared with patients with negative SLNB. In addition, the Breslow index was higher for melanoma of the scalp compared with non-scalp melanoma. The median follow-up was 24.8 months. Progression occurred at the systemic level in the 62.5% of cases. There was a significant association between positive SLNB and progression (p-value p-value: 0.15). Conclusions: Scalp melanomas are more aggressive than other types of H&N melanomas. Sentinel lymph node status is the strongest prognostic criterion for recurrence

Study of the Coupling of Terahertz Radiation to HeterostructureTransistors with a Free Electron Laser Source

High electron mobility transistors can work as room-temperature directdetectors of radiation at frequency much higher than their cutofffrequency. Here, we present a tool based on a Free Electron Lasersource to study the detection mechanism and the coupling of the highfrequency signal into the transistor channel. We performed a mappingover a wide area of the coupling of 0.15 THz radiation to an AlGaN/GaNtransistors with cut-off frequency of 30 GHz. Local,polarization-dependent irradiation allowed us to selectively couple thesignal to the channel either directly or through individual transistorbias lines, in order to study the nonlinear properties of thetransistor channel. Our results indicate that HEMT technology can beused to design a millimeter-wave focal plane array with integratedplanar antennas and readout electronics

The impact of the COVID-19 pandemic on head and neck cancer diagnosis in the Piedmont Region, Italy: interrupted time-series analysis

Background: The COVID-19 pandemic has likely affected the most vulnerable groups of patients and those requiring time-critical access to healthcare services, such as patients with cancer. The aim of this study was to use time trend data to assess the impact of COVID-19 on timely diagnosis and treatment of head and neck cancer (HNC) in the Italian Piedmont region. Methods: This study was based on two different data sources. First, regional hospital discharge register data were used to identify incident HNC in patients ≥18 years old during the period from January 1, 2015, to December 31, 2020. Interrupted time-series analysis was used to model the long-time trends in monthly incident HNC before COVID-19 while accounting for holiday-related seasonal fluctuations in the HNC admissions. Second, in a population of incident HNC patients eligible for recruitment in an ongoing clinical cohort study (HEADSpAcE) that started before the COVID-19 pandemic, we compared the distribution of early-stage and late-stage diagnoses between the pre-COVID-19 and the COVID-19 period. Results: There were 4,811 incident HNC admissions in the 5-year period before the COVID-19 outbreak and 832 admissions in 2020, of which 689 occurred after the COVID-19 outbreak in Italy. An initial reduction of 28% in admissions during the first wave of the COVID-19 pandemic (RR 0.72, 95% CI 0.62–0.84) was largely addressed by the end of 2020 (RR 0.96, 95% CI 0.89–1.03) when considering the whole population, although there were some heterogeneities. The gap between observed and expected admissions was particularly evident and had not completely recovered by the end of the year in older (≥75 years) patients (RR: 0.88, 0.76–1.01), patients with a Romano-Charlson comorbidity index below 2 (RR 0.91, 95% CI: 0.84–1.00), and primary surgically treated patients (RR 0.88, 95% CI 0.80–0.97). In the subgroup of patients eligible for the ongoing active recruitment, we observed no evidence of a shift toward a more advanced stage at diagnosis in the periods following the first pandemic wave. Conclusions: The COVID-19 pandemic has affected differentially the management of certain groups of incident HNC patients, with more pronounced impact on older patients, those treated primarily surgically, and those with less comorbidities. The missed and delayed diagnoses may translate into worser oncological outcomes in these patients

Tailoring of Highly Intense THz Radiation Through High Brightness Electron Beams Longitudinal Manipulation

The ultra-short electron beams, produced through the velocity bunching compression technique at the SPARC_LAB test Facility (Frascati, Italy), are used to produce Coherent Transition Radiation in the terahertz (THz) range. This paper reports on the main features of this THz source, which have a spectral coverage up to 5 THz, a pulse duration down to 100 fs, and an energy per pulse on the order of tens of μJ. These figures of merits open the possibility to apply this source for nonlinear and THz pump-probe experiments in Solid-State Physics and material science