473 research outputs found
Narrowband spectroscopy by all-optical correlation of broadband pulses
High peak power ultrafast lasers are widely used in nonlinear spectroscopy
but often limit its spectral resolution because of the broad frequency
bandwidth of ultrashort laser pulses. Improving the resolution by achieving
spectrally narrow excitation of, or emission from, the resonant medium by means
of multi-photon interferences has been the focus of many recent developments in
ultrafast spectroscopy. We demonstrate an alternative approach, in which high
resolution is exercised by detecting narrow spectral correlations between
broadband excitation and emission optical fields. All-optical correlation
analysis, easily incorporated into the traditional spectroscopic setup, enables
direct, robust and simultaneous detection of multiple narrow resonances with a
single femtosecond pulse.Comment: 5 pages, 4 figures, submitted to PR
FPGA based data acquisition system for COMPASS experiment
This paper discusses the present data acquisition system (DAQ) of the COMPASS
experiment at CERN and presents development of a new DAQ. The new DAQ must
preserve present data format and be able to communicate with FPGA cards. Parts
of the new DAQ are based on state machines and they are implemented in C++ with
usage of the QT framework, the DIM library, and the IPBus technology. Prototype
of the system is prepared and communication through DIM between parts was
tested. An implementation of the IPBus technology was prepared and tested. The
new DAQ proved to be able to fulfill requirements.Comment: 8 pages, CHEP 201
A digital calorimetric trigger for the COMPASS experiment at CERN
In order to provide a trigger for the Primakoff reaction, in 2009, the trigger system of the COMPASS experiment at CERN will be extend by an electromagnetic calorimeter trigger. Since it was decided to gain from various benefits of digital data processing, an FPGA based implementation of the trigger is foreseen, running on the front-end electronics, which are used for data acquisition at the same time. This, however, includes further modification of the existing trigger system to combine the digital calorimeter trigger, with its higher latency, and the analogue trigger signals, which will also make use of digital data processing
New pixelized Micromegas detector for the COMPASS experiment
New Micromegas (Micro-mesh gaseous detectors) are being developed in view of
the future physics projects planned by the COMPASS collaboration at CERN.
Several major upgrades compared to present detectors are being studied:
detectors standing five times higher luminosity with hadron beams, detection of
beam particles (flux up to a few hundred of kHz/mm^2, 10 times larger than for
the present detectors) with pixelized read-out in the central part, light and
integrated electronics, and improved robustness. Studies were done with the
present detectors moved in the beam, and two first pixelized prototypes are
being tested with muon and hadron beams in real conditions at COMPASS. We
present here this new project and report on two series of tests, with old
detectors moved into the beam and with pixelized prototypes operated in real
data taking condition with both muon and hadron beams.Comment: 11 pages, 5 figures, proceedings to the Micro-Pattern Gaseous
Detectors conference (MPGD2009), 12-15 June 2009, Kolympari, Crete, Greece
Minor details added and language corrections don
Measuring the proton spectrum in neutron decay - latest results with aSPECT
The retardation spectrometer aSPECT was built to measure the shape of the
proton spectrum in free neutron decay with high precision. This allows us to
determine the antineutrino electron angular correlation coefficient a. We aim
for a precision more than one order of magnitude better than the present best
value, which is Delta_a /a = 5%.
In a recent beam time performed at the Institut Laue-Langevin during April /
May 2008 we reached a statistical accuracy of about 2% per 24 hours measurement
time. Several systematic effects were investigated experimentally. We expect
the total relative uncertainty to be well below 5%.Comment: Accepted for publication in the Conference Proceedings of the
International Workshop on Particle Physics with Slow Neutrons 2008 held at
the ILL, France. To be published in Nuclear Instruments and Methods in
Physics Research, Section
Triple GEM tracking detectors for COMPASS
The small area tracker of COMPASS, a high-luminosity fixed target experiment at CERN's SPS, includes a set of 20 large-size (31\times 31\,\cm^2) Gas Electron Multiplier (GEM) detectors. Based on gas amplification in three cascaded GEM foils, these devices permit to obtain high gain and good spatial resolution even at very high particle fluxes. A two-coordinate projective readout yields, for each track, highly correlated signal amplitudes on both projections, allowing to resolve multiple hits in high occupancy regions close to the central deactivated area of 5\,\cm diameter. At the same time the material exposed to the beam is minimized. Splitting the amplification in three cascaded stages permits to achieve a gain of , necessary for efficient () detection of minimum ionizing particles on both coordinates, already at relatively moderate voltages across individual GEM foils. As a consequence, the probability of a gas discharge to occur when a heavily ionizing particle enters the detector volume, is reduced by more than an order of magnitude at a given gain compared to the initially foreseen double GEM structure. In conjunction with other strategies resulting from extensive R\&D on discharge phenomena, we were able to further reduce both the triggered by heavily ionizing particles entering the detector volume, this helped to drastically reduce both the energy and the probability of such breakdowns. In order to completely exclude permanent damage to the front-end chip by the rare event of a discharge fully propagating to the readout strips, an external electronic protection circuit is used. The operational characteristics of these detectors were examined both in the laboratory and in the beam, where a spatial resolution for minimum ionizing particles of (46\pm 3)\,\mum and a time resolution of \sim 15\,\ns were achieved. For the 2001 run of COMPASS, a total of 14 triple GEM detectors have been installed. First results from the commissioning phase in the high-intensity beam are presented
- …