Numerical simulation of plasma-chemical reactors

Grigoryev, Yu. N.; Gorobchuk, A. G.

doi:10.1007/3-540-32376-7_13

Cited by 4 publications

(3 citation statements)

References 7 publications

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“…In proportional chambers, the most intense formation of free radicals takes place around anode wires where the electric field reaches 20 -200 kV/cm. Dissociation of CF 4 molecules resulting from the impact of electrons of about 3 -5 eV occurs with formation of the following chemically active radicals [14,15] Thus, to recover MWPCs from ME caused by silicone or organic films on the cathode surface, the corresponding depositions can be etched in the presence of CF 4 . However, in the vicinity of the cathode, which is several millimeters away from the anode wires and the plasma environment, the concentration of fluorine radicals is small.…”

Section: A Curing Malter-like Effects In Mwpc In Presence Of Cfmentioning

confidence: 99%

“…Various studies of dry etching processes showed that the etching rate in a CF 4 /O 2 mixture is significantly higher in comparison to the one in a pure CF 4 plasma [15,16]. Oxygen radicals promote the formation of •COF x , which quickly dissociates in collisions with surrounding electrons and atoms and indirectly increases the number of fluorine radicals in the gas discharge plasma, as shown by the following reactions: Moreover, oxygen itself plays a significant role in polymer film dry etching [17].…”

Section: B Gas Compositon For Accelerated Recovery From Malter Effectmentioning

confidence: 99%

Section: A Curing Malter-like Effects In Mwpc In Presence Of Cfmentioning

confidence: 99%

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Long-term operation of the multi-wire-proportional-chambers of the LHCb muon system

et al. 2019

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The muon detector of LHCb, which comprises 1368 multi-wire-proportional-chambers (MWPC) for a total area of 435 m 2 , is the largest instrument of its kind exposed to such a high-radiation environment. In nine years of operation, from 2010 until 2018, we did not observe appreciable signs of ageing of the detector in terms of reduced performance. However, during such a long period, many chamber gas gaps suffered from HV trips. Most of the trips were due to Malter-like effects, characterised by the appearance of local self-sustained high currents, presumably originating from impurities induced during chamber production. Very effective, though long, recovery procedures were implemented with a HV training of the gaps in situ while taking data. The training allowed most of the affected chambers to be returned to their full functionality and the muon detector efficiency to be kept close to 100%. The possibility of making the recovery faster and even more effective by adding a small percentage of oxygen in the gas mixture has been studied and successfully tested.

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Section: A Curing Malter-like Effects In Mwpc In Presence Of Cfmentioning

confidence: 99%

Section: B Gas Compositon For Accelerated Recovery From Malter Effectmentioning

confidence: 99%

Section: A Curing Malter-like Effects In Mwpc In Presence Of Cfmentioning

confidence: 99%

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Long-term operation of the multi-wire-proportional-chambers of the LHCb muon system

et al. 2019

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Long-term and efficient operation of the MWPC muon detector at LHCb

Kotriakhova

2020

Nuclear Instruments and Methods in Physics Research Section A:

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The Multi-Wire-Proportional-Chamber (MWPC) muon detector of LHCb is one of the largest instrument of this kind worldwide, and one of the most irradiated. All of the MWPCs are supplied with a 40% Ar + 55% CO 2 + 5% CF 4 gas mixture. For most of the LHC operation so far we took data at an instantaneous luminosity of 4 10 32 cm-2 s-1. The most irradiated MWPCs integrated over the past nine years ~0.6 C/cm of charge per unit length of wire. In nine years of MWPCs operation in a high radiation environment, the chambers didn't show a gain reduction or any other apparent symptom of ageing. However, many gas gaps were affected by the sudden appearance of high currents. This effect, originating from localized areas in the individual gaps of the MWPCs, results in an increased noise rate and a trip of the high-voltage (HV) supply system due to a current exceeding the set threshold. The observed phenomenon of currents triggered by high radiation, but self-sustained if beam goes off, suggests that most of the trips are due to Malter-like effects (ME). This phenomenon can be due to thin insulator deposits on the cathode coming from either the construction process, or from polymerization reactions taking place near the anode wires in the gas discharge plasma. During operation of the LHC, about 100 gas gaps were affected every year by HV trips. Most of the problematic chambers could be recovered successfully in situ during data taking under nominal beam conditions by means of a long HV training performed on the affected MWPC gaps. This method has proven to be very effective, allowing recovery of normal operation conditions for most of the MWPC gaps affected by HV trips, so that the muon detection efficiency could be kept close 100%. This is a remarkable result, since the recovery of gas discharge detectors without disassembling is topical for many modern experiments.

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Numerical Investigation of O2 Adsorption Effect in Si - CF4/O2 System

Grigoryev

Gorobchuk

2006 25th International Conference on Microelectronics

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Numerical simulation of plasma-chemical reactors

Cited by 4 publications

References 7 publications

Long-term operation of the multi-wire-proportional-chambers of the LHCb muon system

Long-term operation of the multi-wire-proportional-chambers of the LHCb muon system

Long-term and efficient operation of the MWPC muon detector at LHCb

Numerical Investigation of O2 Adsorption Effect in Si - CF4/O2 System

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