18 research outputs found
Response of a CMS HGCAL silicon-pad electromagnetic calorimeter prototype to 20-300 GeV positrons
The Compact Muon Solenoid Collaboration is designing a new high-granularity
endcap calorimeter, HGCAL, to be installed later this decade. As part of this
development work, a prototype system was built, with an electromagnetic section
consisting of 14 double-sided structures, providing 28 sampling layers. Each
sampling layer has an hexagonal module, where a multipad large-area silicon
sensor is glued between an electronics circuit board and a metal baseplate. The
sensor pads of approximately 1 cm are wire-bonded to the circuit board and
are readout by custom integrated circuits. The prototype was extensively tested
with beams at CERN's Super Proton Synchrotron in 2018. Based on the data
collected with beams of positrons, with energies ranging from 20 to 300 GeV,
measurements of the energy resolution and linearity, the position and angular
resolutions, and the shower shapes are presented and compared to a detailed
Geant4 simulation
Performance of the CMS High Granularity Calorimeter prototype to charged pion beams of 20300 GeV/c
The upgrade of the CMS experiment for the high luminosity operation of the
LHC comprises the replacement of the current endcap calorimeter by a high
granularity sampling calorimeter (HGCAL). The electromagnetic section of the
HGCAL is based on silicon sensors interspersed between lead and copper (or
copper tungsten) absorbers. The hadronic section uses layers of stainless steel
as an absorbing medium and silicon sensors as an active medium in the regions
of high radiation exposure, and scintillator tiles directly readout by silicon
photomultipliers in the remaining regions. As part of the development of the
detector and its readout electronic components, a section of a silicon-based
HGCAL prototype detector along with a section of the CALICE AHCAL prototype was
exposed to muons, electrons and charged pions in beam test experiments at the
H2 beamline at the CERN SPS in October 2018. The AHCAL uses the same technology
as foreseen for the HGCAL but with much finer longitudinal segmentation. The
performance of the calorimeters in terms of energy response and resolution,
longitudinal and transverse shower profiles is studied using negatively charged
pions, and is compared to GEANT4 predictions. This is the first report
summarizing results of hadronic showers measured by the HGCAL prototype using
beam test data.Comment: To be submitted to JINS
Linac4 H<sup>-</sup> source R&D: Cusp free ICP and magnetron discharge
The 2MHz radio-frequency inductively coupled plasma heating (ICP RF) of Linac4âs IS03 H-
source is more
efficient without its octupole cusp in offset hallbach configuration. This was shown by Particle in cell Monte-Carlo (PICMC) simulation using the NINJA software [1] and confirmed by plasma characterization via optical emission spectroscopy
[2,3], an easier plasma ignition is also anticipated. In this paper, we present preliminary results of an Alumina plasma
chamber IS03 H-
source [4] operated without magnetic cusp. Operation under monthly cesiation induces a slow evolution
of the molybdenum cesiated surface correlated with an increase of the co-extracted electron yield. An improved stability
of the extracted H-
beam is achieved by compensating the Cs-losses.
The high intensity option for Linac4 features an adaptation of BNLâs Magnetron. Simulation of this complex H2-Cs arc
discharge plasma, where electrons are emitted from a cesiated molybdenum cathode, requires characterization of the plasma
impedance and knowledge of hydrogen and cesium densities. We present a measurement of plasma impedance over the
range of discharge current, hydrogen and cesium-densities
Status and Operation of the Linac4 Ion Source Prototypes
CERNâs Linac4 45 kV H- ion sources prototypes are installed at a dedicated ion source test stand and in the Linac4 tunnel. The operation of the pulsed hydrogen injection, RF sustained plasma and pulsed high voltages are described. The first experimental results of two prototypes relying on 2MHz RF- plasma heating are presented. The plasma is ignited via capacitive coupling, and sustained by inductive coupling. The light emitted from the plasma is collected by viewports pointing to the plasma chamber wall in the middle of the RF solenoid and to the plasma chamber axis. Preliminary measurements of optical emission spectroscopy and photometry of the plasma have been performed. The design of a cesiated ion source is presented. The volume source has produced a 45 keV H- beam of 16-22 mA which has successfully been used for the commissioning of the LEBT, RFQ and chopper of Linac4
CERNâs Linac4 cesiated surface H source
Linac4 cesiated surface H sources are routinely operated for the commissioning of the CERNâs Linac4 and on an ion source test stand. Stable current of 40-50â
mA are achieved but the transmission through the LEBT of 80% was below expectations and triggered additional beam simulation and characterization. The H beam profile is not Gaussian and emittance measurements are larger than simulation. The status of ongoing development work is described; 36â
mA H and 20â
mA D beams were produced with a 5.5â
mm aperture cesiated surface ion source. The emittances measured at the test stand are presented. During a preliminary test, the Linac4 proton source delivered a total beam intensity of 70â
mA (p, H2, H3)
Linac4 Hâ ion sources
CERNâs 160 MeV Hâlinear accelerator (Linac4) is a key constituent of the injector chain upgrade of the Large Hadron Collider that is being installed and commissioned. A cesiated surface ion source prototype is being tested and has delivered a beam intensity of 45 mA within an emittance of 0.3 Ï â
mm â
mrad. The optimum ratio of the co-extracted electron- to ion-current is below 1 and the best production efficiency, defined as the ratio of the beam current to the 2 MHz RF-power transmitted to the plasma, reached 1.1 mA/kW. The Hâsource prototype and the first tests of the new ion sourceoptics, electron-dump, and front end developed to minimize the beam emittance are presented. A temperature regulated magnetron Hâsource developed by the Brookhaven National Laboratory was built at CERN. The first tests of the magnetron operated at 0.8 Hz repetition rate are described
Construction and commissioning of CMS CE prototype silicon modules
As part of its HL-LHC upgrade program, the CMS Collaboration is developing a High Granularity Calorimeter (CE) to replace the existing endcap calorimeters. The CE is a sampling calorimeter with unprecedented transverse and longitudinal readout for both electromagnetic (CE-E) and hadronic (CE-H) compartments. The calorimeter will be built with 30,000 hexagonal silicon modules. Prototype modules have been constructed with 6-inch hexagonal silicon sensors with cell areas of 1.1 , and the SKIROC2-CMS readout ASIC. Beam tests of different sampling configurations were conducted with the prototype modules at DESY and CERN in 2017 and 2018. This paper describes the construction and commissioning of the CE calorimeter prototype, the silicon modules used in the construction, their basic performance, and the methods used for their calibration
The DAQ system of the 12,000 Channel CMS High Granularity Calorimeter Prototype
The CMS experiment at the CERN LHC will be upgraded to accommodate the 5-fold increase in the instantaneous luminosity expected at the High-Luminosity LHC (HL-LHC). Concomitant with this increase will be an increase in the number of interactions in each bunch crossing and a significant increase in the total ionising dose and fluence. One part of this upgrade is the replacement of the current endcap calorimeters with a high granularity sampling calorimeter equipped with silicon sensors, designed to manage the high collision rates. As part of the development of this calorimeter, a series of beam tests have been conducted with different sampling configurations using prototype segmented silicon detectors. In the most recent of these tests, conducted in late 2018 at the CERN SPS, the performance of a prototype calorimeter equipped with of silicon sensors was studied with beams of high-energy electrons, pions and muons. This paper describes the custom-built scalable data acquisition system that was built with readily available FPGA mezzanines and low-cost Raspberry PI computers