RESUMO
Multikilojoule petawatt lasers using chirped-pulse amplification are being constructed worldwide. Several systems have adopted a tiled-grating approach to meet the size requirements for the compression gratings. Grating tiles need to be precisely phased to ensure a transform-limited focal spot when focusing high-energy laser pulses in the target plane. A computer-control test system that uses a Mach-Zehnder interferometer capable of monitoring and correcting drift in the tiled-grating assemblies within the compressor is described. The differential errors due to eight gratings, within a compressor with four grating assemblies, were compensated by adjusting a single grating.
RESUMO
The measured pseudorapidity distribution of primary charged particles in minimum-bias d+Au collisions at sqrt[s(NN)]=200 GeV is presented for the first time. This distribution falls off less rapidly in the gold direction as compared to the deuteron direction. The average value of the charged particle pseudorapidity density at midrapidity is
RESUMO
We have measured transverse momentum distributions of charged hadrons produced in d+Au collisions at sqrt[s(NN)]=200 GeV. The spectra were obtained for transverse momenta 0.25
RESUMO
This paper describes the measurement of collective flow for charged particles in Au+Au collisions at sqrt[s(NN)]=130 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider (RHIC). The measured azimuthal hit anisotropy is presented over a wide range of pseudorapidity (-5.0
RESUMO
We have measured the ratios of antiparticles to particles for charged pions, kaons, and protons near mid-rapidity in central Au+Au collisions at sqrt[s(NN)] = 130 GeV. We observe / = 0.60+/-0.04(stat)+/-0.06(syst). The / ratios give a consistent estimate of the baryo-chemical potential mu(B) of 45 MeV, a factor of 5-6 smaller than in central Pb+Pb collisions at sqrt[s(NN)] = 17.2 GeV.
RESUMO
The charged-particle pseudorapidity density dN(ch)/d eta has been measured for Au+Au collisions at sqrt[s(NN)] = 130 GeV at RHIC, using the PHOBOS apparatus. The total number of charged particles produced for the 3% most-central Au+Au collisions for /eta/
RESUMO
Digital pulse processing is a signal processing technique in which detector (preamplifier output) signals are directly digitized and processed to extract quantities of interest. This approach has several significant advantages compared to traditional analog signal shaping. First, analyses can be developed which take pulse-by-pulse differences into account, as in making ballistic deficit compensations. Second, transient induced charge signals, which deposit no net charge on an electrode, can be analyzed to give, for example, information on the position of interaction within the detector. Third, deadtimes from transient overload signals are greatly reduced, from tens of micros to hundreds of ns. Fourth, signals are easily captured, so that more complex analyses can be postponed until the source event has been deemed "interesting". Fifth, signal capture and processing may easily be based on coincidence criteria between different detectors or different parts of the same detector. XIAs recently introduced CAMAC module, the DGF-4C, provides many of these features for four input channels, including two levels of digital processing and a FIFO for signal capture for each signal channel. The first level of digital processing is "immediate", taking place in a gate array at the 40 MHz digitization rate, and implements pulse detection, pileup inspection, trapezoidal energy filtering, and control of an external 25.6 micros long FIFO. The second level of digital processing is provided by a digital signal processor (DSP), where more complex algorithms can be implemented. To illustrate digital pulse processing's possibilities, we describe the application of the DGF-4C to a series of experiments. The first, for which the DGF was originally developed, involves locating gamma-ray interaction sites within large segmented Ge detectors. The goal of this work is to attain spatial resolutions of order 2 mm sigma within 70 mm x 90 mm detectors. We show how pulse shape analysis allows ballistic deficit to be significantly reduced in these detectors. A second experiment involves studying exotic nuclei by observing their 1 MeV direct proton decays following implantation in a Si crossed stripe detector at 35 MeV. Whereas the implantation paralyzes analog electronics for almost 10 micros, the DGF allows the study of decay times as short as 1 micros. Initial energy and time resolution results are presented. Finally, we show how the DGF's precise timing and coincidence capabilities lead to significant experimental simplifications in dealing with phoswich detectors, low background counting work, and trace Pb detection by coincident photon detection.
