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Page 1: K p - bo.infn.it · ` d [ 12 C F liquid radiator 6 14 light Cherenkov light Cherenkov electrons photo C F gas radiator UV photon detector 5 particle mirror ' (*`,-b

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Page 2: K p - bo.infn.it · ` d [ 12 C F liquid radiator 6 14 light Cherenkov light Cherenkov electrons photo C F gas radiator UV photon detector 5 particle mirror ' (*`,-b

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64 CHAPTER 4 THE RICH DETECTORS AT DELPHI

Figure 4.5. The layout of the forward RICH.

a Bhabha event.In 1994 it was noticed that there was a sizable leak between the liquid and

gas radiator systems. This was noticed as an instability of the refractive index.Since it jeopardized the security and stability of the system, a distillation plantwas installed in 1995, designed to separate C F and C F [71].

4.2.2 Forward detector

Each forward end-cap consists of 12 sectors in as illustrated in figure 4.5. Asingle sector is made up of 3 liquid radiators, 1 gas radiator, 2 drift-chambersand 5 spherical mirrors. The liquid radiators have the same liquid and thick-ness as those of the barrel. For the gas radiator, however, C F is used insteadof C F . It has a small disadvantage of having a slightly lower refractive in-dex thus yielding fewer photons. This is compensated by the fact that the gasradiator is thicker ( cm). An advantage is the low boiling point of about

C, which allows the forward detector to be operated at ambient tempera-ture. The drift chambers have ethane as drift gas, doped with TMAE.

As mentioned before, the forward RICH has the magnetic field perpendic-

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Page 19: K p - bo.infn.it · ` d [ 12 C F liquid radiator 6 14 light Cherenkov light Cherenkov electrons photo C F gas radiator UV photon detector 5 particle mirror ' (*`,-b

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