Gas Systems for High Energy Physics Detectors
Creation of the New Gas Systems Generation for the Future Detectors of STAR and PHENIX Experiments at Brookhaven National Laboratory
Tech Area / Field
- PHY-ANU/Atomic and Nuclear Physics/Physics
- PHY-PFA/Particles, Fields and Accelerator Physics/Physics
3 Approved without Funding
Nuclear Physics Institute, Russia, Leningrad reg., Gatchina
- Brookhaven National Laboratory / Physics Department, USA, NY, Upton
Project summaryThe main aim of the project is creation of two recovery system for the components of the gas mixtures (90% R134a + 5% i-Butane + 5% SF6) and (94.5% R134a + 5% i Butane + 0.5% SF6) for the detectors under construction in STAR and PHENIX experiments at RHIC accelerator in Brookhaven National Laboratory, USA. These systems have to be connected to the main circulation gas systems of the detectors in the point of gas mixture withdrawal to the atmosphere and intended for collecting and separation of all withdrawn mixture. The results of the project are very important for the high energy physics detectors development, because they allow to reduce pure gas expenses as well as prevent withdrawal of the environmentally dangerous gases to the atmosphere.
STAR and PHENIX experiments at RHIC collider at Brookhaven National Laboratory (BNL, USA) are planning the installation of the new detectors in 2007-2008. STAR experiment will install Time of Flight (TOF) detector and PHENIX – also TOF and forward Resistive Plate Chambers (RPC). TOF detectors will use 90% R134a + 5% i-Butane + 5% SF6 mixture and forward RPC will be supplied with 94.5% R134a + 5% i-Butane + 0.5% SF6 mixture. USA Environmental Protection Agency identified Sulfur Hexafluoride (SF6) as a strong greenhouse gas and its penetration to the atmosphere must be restricted. With a global warming potential 23900 times greater than CO2 and an atmospheric life of 3200, one kilogram of SF6 has the same global warming impact of 22 tons of CO2. Thus, all SF6 gas injected into the system has to be recovered.
Present gas systems, which are widely used in STAR and PHENIX experiments, were designed and fabricated by Cryogenic and Superconductive Technique Department of Petersburg Nuclear Physics Institute as closed gas loops with a small amount of mixture venting to the atmosphere [1, 2, 3]. The gas mixtures for these detectors do not contain the components like SF6. Therefore the new gas system design has to include the recovery system. Such system should be considered not only to recover SF6 but also expensive Freon 134a and i-Butane. It means that the gas system has to be a close loop system with a possibility to recover all withdrawn mixture.
A proposed gas system design shown in Fig. 1 is suitable for both TOF and RPC detectors. It is pided by two parts: TOF/RPC circulation gas system and the recovery system. The first part is responsible for the TOF/RPC detector supply with the correct mixture content providing the stable differential pressure. The second part is used for withdrawn mixture recovery and separation for the recycling.
The recovery system is based on the adsorption principle. Activated carbon is a very nice adsorbent to catch Freon 134a. Approximately 0.8 gram of Freon 134a can be adsorbed with 1 gram of activated carbon at room temperature and pressure slightly more than atmospheric . Sulfur Hexafluoride (SF6) and i-Butane adsorption by activated carbon is much less than Freon 134a at room temperature and low pressure. It means that the carbon can separate Freon 134a from SF6 and i-Butane.
Preliminary estimation of the recovery system benefit for the PHENIX experiment shows that the usage of such system allows to save up to $30,000.00 per 5 months run and recover about 80 kg of SF6 which will not be vented to the atmosphere. Therefore, more than $350,000.00 could be saved for two systems during 7-8 years of operation.
The research and development program contains various investigations:
- The influence of Joule-Thompson throttle effect on the adsorption heat for Freon 134a and working mixtures in the temperature range of -20ºC ÷ +40ºC.
- Adsorption data for i-Butane and SF6 on the activated carbon in the temperature range of -20ºC ÷ +40ºC and partial pressures below 1 bar.
- Solubility of SF6 in i-Butane investigation.
- Work through the chromatographic measurement procedure of the Freon content in the working mixtures.
- Investigation of various versions of SF6+iButane mixture separation.
- The adsorption compressor performance measurements and choice of the compressor type for the recovery system (dry piston, membrane or adsorption).
The Laboratory of Cryogenic and Superconductive Techniques, which will be engaged into the project has the great experience in the circulation gas system development, gas purification, cryogenic techniques and cooling systems, and the charged particles beams as well. The experience is based on the previous works in the military technologies. Navigation techniques and the material irradiation of the materials by 1 GeV protons (energy is close to the protons energy in the radiation earth sphere). Participation of the scientists in this project will be very useful for the integration jf the military scientists in the international physics community and the orientation of them on peaceful activity. In addition to the main aim, the project has supplementary result, as long as it prevents penetration of the environmentally dangerous gases to the atmosphere.
- L.Kotchenda et al. STAR TPC Gas System. NIM A 499, 703 (2003).
- L.Kotchenda et al. PHENIX Muon Tracking Detector Gas System. Preprint PNPI 2594, Gatchina, 2005.
- L.Kotchenda et al. Gas systems for PHENIX and STAR detectors. PNPI Annual Report 2005.
- C.Christy, R.Toosi. Adsorption Air-Conditioning for Containerships and Vehicles. Metrans Report 00-7.August 05.2004.
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