The laser system for the STAR time projection chamber

Abstract

The Time Projection Chamber (TPC) is the core tracking detector for the STAR experiment at RHIC. To determine spatial distortions, calibrate and monitor the TPC, a laser calibration system has been built. We developed a novel design to produce ~500 thin laser beams simulating straight particle tracks in the TPC volume. The new approach is significantly simpler than the traditional ones, and provides a higher TPC coverage at a reduced cost. During RHIC 2000 and 2001 runs the laser system was used to monitor the TPC performance and measure drift velocity with ~0.02 % accuracy. Additional runs were recorded with and without magnetic field to check ExB corrections.

The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events

“…Many features of the ALICE laser calibration system follow the system built and operated by the STAR experiment at RHIC [45,46].…”

“…Energetic pulsed laser light in the UV region is obtained from a Nd:YAG laser (λ = 1064 nm) equipped with two frequency doublers, generating pulses of UV light of 266 nm wavelength. The same kind of laser was used for the STAR experiment at RHIC [46], and also in NA49 [7] and CERES/NA45 [48] at the CERN SPS and ALEPH [49] at LEP. The typical beam diameter from this kind of laser is 9-10 mm, but our lasers were fitted with telescopes to expand the beam diameter to about 25 mm.…”

Investigation of UV laser ionisation in argon-based gas mixtures with a Triple-GEM detector

“…Gases mainly used in TPCs are studied in this experiment, including P10 gas (Ar:CH 4 = 90:10) [5], a mixture of argon and carbon dioxide (Ar:CO 2 = 90:10) and a fast gas mixture called T2K (Ar:CF 4 :iC 4 H 10 = 95:3:2) [11]. The purities of argon, carbon dioxide, methane, and carbon tetrafluoride is up to 99.999%, and the purity of isobutane is 99.9% as shown in table 1.…”

“…There have already been several experiments applying laser calibration systems. In ALEPH, the laser system is used to measure the drift velocity, ωτ and the azimuthal coordinate shifts [4].The STAR TPC adopts a novel design to produce 252 laser beams uniformly distributed in each half of the TPC for calibration and has measured the drift velocity with 0.02% accuracy successfully [5]. A Nd:YAG laser, which wavelength is quadruped to 266 nm, is used in the experiment.…”

Estudo da produção de quarks pesados no experimento STAR@RHIC

“…A figura 2.16, também retirada da referência [37], revela uma A velocidade | v D | é então calculada durante a tomada de dados. Em intervalos de algumas horas, iniciam-se tomadas de dados utilizando-se de laseres dentro do TPC [39]. Os laseres funcionam como partículas que atravessam o detector ionizando a gás.…”