Ageing in the LHCb outer tracker: Aromatic hydrocarbons and wire cleaning Tuning, N.; Bachmann, S.; Bagaturia, Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2011, Letnik:
656, Številka:
1
Journal Article
Recenzirano
The LHCb Outer Tracker straw tubes have shown to suffer from gain loss after irradiation in the laboratory at moderate intensities. Under irradiation an insulating layer is formed on the anode wire. ...The ageing is caused by contamination of the counting gas due to outgassing of the plastifier di-isopropyl-naphthalene in araldite AY103-1 used at construction. This paper presents irradiation results with and without the plastifier, together with the mass spectra of the glue samples. In addition, the effects of wire heating and large currents are presented.
The LHCb Outer Tracker (OT) detector has shown to suffer from gain loss after irradiation in the laboratory at moderate intensities. Under irradiation an insulating layer is formed on the anode wire. ...The ageing is caused by contamination of the counting gas due to outgassing of the glue used in construction namely araldite AY103-1. The gain loss is concentrated upstream the gas flow, and at moderate irradiation intensity only. The ageing rate is reduced by longterm flushing and by the addition of a few percent of
O
2
to the gas mixture. Furthermore, applying a large positive high voltage (beyond the amplification regime) removes the insulating deposits without damaging the wire surface. This paper presents both the characteristics of the ageing phenomenon and the beneficial treatments.
The results of 5 years of development of the inner tracking system of the HERA-B experiment and first experience from the data taking period of the year 2000 are reported. The system contains 184 ...chambers, covering a sensitive area of about
(20×20)
cm
2
each. The detector is based on microstrip gas counters (MSGCs) with diamond-like coated (DLC) glass wafers and gas electron multipliers (GEMs). The main problems in the development phase were gas discharges in intense hadron beams and aging in a high radiation dose environment. The observation of gas discharges which damage the electrode structure of the MSGC led to the addition of the GEM as a first amplification step. Spurious sparking at the GEM cannot be avoided completely. It does not affect the GEM itself but can produce secondary damage of the MSGC if the electric field between the GEM and the MSGC is above a threshold depending on the operation conditions. We observed that aging does not only depend on the dose but also on the spot size of the irradiated area. Ar–DME mixtures had to be abandoned whereas a mixture of 70% Ar and 30% CO
2 showed no serious aging effects up to about
40
mC
/cm deposited charge on the anodes. X-ray measurements indicate that the DLC of the MSGC is deteriorated by the gas amplification process. As a consequence, long-term gain variations are expected. The Inner Tracker has successfully participated in the data taking at HERA-B during summer 2000.
The production of K_short mesons in pp collisions at a centre-of-mass energy of 0.9 TeV is studied with the LHCb detector at the Large Hadron Collider. The luminosity of the analysed sample is ...determined using a novel technique, involving measurements of the beam currents, sizes and positions, and is found to be 6.8 +/- 1.0 microbarn^-1. The differential prompt K_short production cross-section is measured as a function of the K_short transverse momentum and rapidity in the region 0 < pT < 1.6 GeV/c and 2.5 < y < 4.0. The data are found to be in reasonable agreement with previous measurements and generator expectations.
PDF
