Studies of helium gas mixtures in drift chambers

Abstract

Some properties of gas mixtures, composed predominately of helium and lesser amounts of CO2 and isobutane, were measured in a prototype drift chamber. The studies are motivated by the desire to reduce the multiple scattering inside the drift chamber at future high-luminosity, low-energy facilities such as 4 factories, T/charm factories, and B factories. The low atomic number of helium greatly reduces the multiple scattering contribution to the momentum resolution compared to an argon-based gas mixture. The position resolution, pulse height, efficiency, and breakdown characteristics were measured for various gas mixtures. A mixture of 83% He, 10% CO2, and 7% isobutane gives comparable results to that of an argon-based gas commonly used in drift chambers.

Measurement of electron drift parameters for helium and CF4-based gases

“…Even so, such DME gas mixtures are not as effective in preventing breakdown as, for example, 78% He •t 15% CO2 + 7% i&HI0 (see table 1 for the breakdown limits). This gas was also studied in a large tracking chamber by a group using an old Mark II prototype at SLAC [42]. Recently, other groups have also performed studies with He-based gases [37,43].…”

Measurement of the Inclusive Branching FractionsB(B^- to D⁺ π^- π^-) and B(B^- to D^{*^+} π^- π^-)

“…The Drift Chamber (DCH) (Figure 2.8) is another sub-detector that detects charged particle trajectories. As a charged particle passes through the DCH [29], it leaves an ionization trail. The ionization charge drifts to sense wires due to strong local electric fields.…”

“…These wires are contained in a mixture of 80% helium and 20% isobutane gas. The helium is used to reduce multiple scattering [29,30]. The layers are grouped by fours into 10 sets of layers.…”

“…Figure 1.2 and Table 1.2 show the spectroscopy of D 0 J . The two D 0 J mesons with j = 1 2 states have broad (a few hundred MeV) resonances while the two j = 3 2 states have narrow resonances (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30). Further discussion of the S and D wave decays is presented in Chapter 3.…”

Experimental Study of Three-body Cabibbo-suppressed D0 Decays and Extraction of Cp Violation Parameters

“…Longitudinal information is derived from wires placed at small angles to the principal axis. The helium/isobutane gas mixture reduces the scattering and improves the measurement of low momentum tracks [16].…”