Direct measurement of the formation length of photons

We report the first observation of a shoulder in the radiation spectrum from GeV electrons in a structured target consisting of two thin and closely spaced foils. The position of the shoulder depends on the target spacing and is directly connected to the finite formation length of a low-energy photon emitted by an ultrarelativistic electron.With the present setup it is possible to control the separation of the foils on a m scale and hence measure interference effects caused by the macroscopic dimensions of the formation length. Several theoretical groups have predicted this effect using different methods. Our observations have a preference for the modified theory by Blankenbecler but disagree with the results of Baier and Katkov

A dedicated setup for the measurement of the electron transport parameters in gases at large electric fields

Electron transport parameters are important in several areas ranging from particle detectors to plasma-assisted processing reactors. Nevertheless, especially at high fields strengths and for complex gases, relatively few data are published. A dedicated setup has been developed to measure the electron drift velocity and the first Townsend coefficient in parallel plate geometry. An RPC-like cell has been adopted to reach high field strengths without the risk of destructive sparks. The validation data obtained with pure Nitrogen will be presented and compared to a selection of the available literature and to calculations performed with Magboltz 2 version 8.6. The new data collected in pure Isobutane will then be discussed. This is the first time the electron drift velocity in pure Isobutane is measured well into the saturation region. Good agreement is found with expectations from Magboltz. (C) 2009 Elsevier B.V. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP[02/04697-1]FAPESP[06/58855-8]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP[07/50591-4]FCTFundação para a Ciência e a Tecnologia de Portugal (FCT)EUEUFEDERFondo Europeo de Desarrollo Regional (FEDER)POCI[POCI/FP/81981/2007]POC

Lights and (some) shadows in the comparison among experimental data of heavy ion collisionat Fermi energies and the dynamical model AMD

The simulation of heavy ion collisions in the Fermi energy region is a challenge for the theoretical models; in particular it is difficult to obtain a coherent description in all the impact parameter range and to reproduce all the experimental observables. In this contribution we will show the very good job done by the dynamical model AMD [1] followed by the statistical code GEMINI [2, 3] as an afterburner. The model is able to reproduce the main characteristics of peripheral and semiperipheral collisions, although some discrepancies still persist

Lights and (some) shadows in the comparison among experimental data of heavy ion collisionat Fermi energies and the dynamical model AMD

The simulation of heavy ion collisions in the Fermi energy region is a challenge for the theoretical models; in particular it is difficult to obtain a coherent description in all the impact parameter range and to reproduce all the experimental observables. In this contribution we will show the very good job done by the dynamical model AMD [1] followed by the statistical code GEMINI [2, 3] as an afterburner. The model is able to reproduce the main characteristics of peripheral and semiperipheral collisions, although some discrepancies still persist

The MBRD Dipoles for the Luminosity Upgrade at the LHC: From Prototype Tests to the Series Production

The recombination dipoles MBRD for the High Luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN are double-aperture superconducting magnets generating a central magnetic field of 4.5 T in a 105 mm diameter bore, directed in the same direction in both apertures. The integrated magnetic field is 35 T-m in a magnetic length of 7.78 m: with respect to the corresponding magnet presently installed in LHC, the aperture is larger, the length is smaller and the central field is higher. The project, currently underway, includes the fabrication by ASG Superconductors and testing at CERN of a short model (1.6 m long), a prototype, and a series of 4 + 2 spare dipoles. The short model was delivered to CERN and successfully tested in a vertical cryostat in summer 2020, reaching nominal current after three quenches in the second thermal cycle, validating most of the mechanical, thermal and electrical design and giving indications for improvements that have been implemented in the prototype, which was completed and delivered to CERN in October 2021. It was tested in October 2022 in its final cold mass, 14 m long, which also includes the two orbit correctors. This contribution reports on key results from the prototype tests and on the further activities related to the construction of the first magnets of the series

The Development of MBRD Magnets, the Separation/Recombination Dipoles for the LHC High Luminosity Upgrade

As part of the high-luminosity upgrade of CERN LHC accelerator project, the National Institute of Nuclear Physics (INFN) in Genoa, Italy, has developed the MBRD separation-recombination dipole, also known as D2, whose function is to bring beams into collision before and after the interaction regions of the CMS and ATLAS experiments. It is a NbTi cos-theta double aperture dipole that generates a 4.5 T field in a 105 mm aperture, with a magnetic length of 7.78 m, and has the specific feature that the magnetic field in the two apertures is oriented in the same direction. The agreements between INFN and CERN, signed in 2016 and 2020, called for the construction of a short model, 1.6 m long, a prototype of final size, and the six series magnets, four of which are to be installed in the tunnel and two spare. After an international tender, the construction of all magnets was awarded to ASG Superconductors. The short model was successfully tested at CERN in a vertical cryostat in August 2020, reaching nominal current after three quenches in the second thermal cycle, validating most of the mechanical, thermal, and electrical design and providing important insights into the improvements that were implemented in the prototype. Testing of the D2 cold mass prototype was performed in October 2022. Its performance was found to be extremely good, with no quenches below nominal current even in the first thermal cycle and showing excellent operating margin in terms of current, ramp rate, and temperature. Although the series magnets were designed to be identical to the prototype, some modifications and tuning improvements, including a small cross-sectional refinement, were implemented and assessed with the construction of the first magnet in the series. This contribution reports all the activities that, based on the short model and prototype experience, led us to the construction of the first series magnet