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| Main Authors: | , , , , |
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| Format: | Preprint |
| Published: |
2024
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2403.12178 |
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| _version_ | 1866929281557331968 |
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| author | Wendisch, Christian Muentz, Christian Lopes, Luis Schwab, Erwin Stroth, Joachim |
| author_facet | Wendisch, Christian Muentz, Christian Lopes, Luis Schwab, Erwin Stroth, Joachim |
| contents | The central tracking system of the HADES detector, installed at the SIS-18 synchrotron at GSI/Darmstadt (Germany), employs large-area, low-mass drift chambers, featuring Aluminum potential wires and small cell sizes. The chambers in front of the magnetic field, closest to the interaction point, have developed significant self-sustained currents and discharges during operation, most probably triggered by isobutane-based gas mixtures. Only both, (i) replacing isobutane by CO2 and (ii) adding 1000 to 3500 ppmv of water into the Ar/CO2 counting gas mixture, individually optimized for a given chamber, allowed to recover the chambers, enabling stable operation in several production runs since then, e.g. with high-intensity heavy-ion induced reactions. The origin of the instability was found to be deposits on the cathode wires, provoking the Malter-like effects, by visual inspection and energy-dispersive X-ray spectroscopy. The charge on the wires accumulated during their lifetime does not point to so-called classical aging, but presumably the interaction of isobutane with materials in the gas flow, residual impurities, and reaction products formed in plasma, e.g., built by discharges. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2403_12178 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Recovery of HADES drift chambers suffering from Malter-like effects Wendisch, Christian Muentz, Christian Lopes, Luis Schwab, Erwin Stroth, Joachim Instrumentation and Detectors The central tracking system of the HADES detector, installed at the SIS-18 synchrotron at GSI/Darmstadt (Germany), employs large-area, low-mass drift chambers, featuring Aluminum potential wires and small cell sizes. The chambers in front of the magnetic field, closest to the interaction point, have developed significant self-sustained currents and discharges during operation, most probably triggered by isobutane-based gas mixtures. Only both, (i) replacing isobutane by CO2 and (ii) adding 1000 to 3500 ppmv of water into the Ar/CO2 counting gas mixture, individually optimized for a given chamber, allowed to recover the chambers, enabling stable operation in several production runs since then, e.g. with high-intensity heavy-ion induced reactions. The origin of the instability was found to be deposits on the cathode wires, provoking the Malter-like effects, by visual inspection and energy-dispersive X-ray spectroscopy. The charge on the wires accumulated during their lifetime does not point to so-called classical aging, but presumably the interaction of isobutane with materials in the gas flow, residual impurities, and reaction products formed in plasma, e.g., built by discharges. |
| title | Recovery of HADES drift chambers suffering from Malter-like effects |
| topic | Instrumentation and Detectors |
| url | https://arxiv.org/abs/2403.12178 |