Information on C4F10 systems...........

Forward RICH of DELPHI

-   *Evolution of the transparency of C4F10 in the Forward RICH of
    DELPHI* (5.22.00)

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-   Original gas was cleaned by molecular sieves to get rid of water

    -   Transmittance spectra fell for wavelengths lower than 1950 A

    -   Used 13X molecular sieve

-   Massive use of activated carbon in addition to molecular sieves
    raised transmittance to good levels

    -   Took 1.5 kg of carbon to clean 8 liquid liters of C4F10

-   Fabry-Perot interferometer used to measure refractive index

-   Operated at ambient temperature

-   Sound velocity measurement allowed determination of C4F10 amount in
    mixture

    -   Claimed to be cheap and reliable

-   Used massive amounts of molecular sieves and activated carbon

COMPASS RICH

-   *The COMPASS RICH project* (10.23.99)

-   Gas RICH with 3 m long C4F10 radiator, atm. Pressure, 25 ^o^C

-   Goal was water vapor and oxygen traces below 5 ppm

-   H2O and O2 removed using molecular sieves and C4F10 and N2
    separation is obtained with a liquifier

-   Gas flow was 1 volume every 8 hrs.

-   Temperature stability at +/- 1^o^C.

-   *COMPASS RICH-1* (3.13.01)

-   Filling and emptying show gas replacement at 97% level.

LHCb RICH

-   *LHCb RICH Gas System Proposal* (8.6.00)

-   RICH 1 filled with 4 m^3^ of C4F10.

-   Gas systems will run as closed loop circulation with a gas recovery
    system.

    -   Inline liquefaction of return gas to separate volatile
        impurities

    -   C4F10 enters the separation system with N2/O2 and will be
        pre-cooled while passing the return gas thru 2 heat exchangers.

    -   C4F10 cooled down to --50 ^o^C

    -   Pure C4F10 is then collected and transferred to a reservoir
        which serves as a supply for the RICH

    -   N2/O2 leave thru exhaust

    -   Pump in return line compresses gas before entering the
        separation plant

    -   C4F10 will be liquid behind the compressor

-   Oxygen and water not too exceed 100-200 ppm

    -   Molecular sieve used to reduce water impurities along with
        activated carbon

    -   3X and 4X sieves also used

    -   Gas analysis before and after purification

-   Residual nitrogen has an effect on refractive index and should be
    kept constant and below 1%

-   The gases are circulated in a closed loop with an expected flow rate
    of 10% of the total gas volume.

-   Two gas inlets/two gas outlets

    -   C4F10 from bottom and N2 from top

-   *Monitoring, Alignment and Control of the RICH Detectors* (9.6.00)

-   Refractive index depends upon temperature and pressure

-   Gases are clean from trace impurities after 1 week of recirculation

-   Ultrasonic sonar measures variations in the refractive index due to
    increased concentrations of nitrogen in the system

-   Monochromator measures transparency

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-   <http://dustbunny.physics.indiana.edu/~dzierba/pidtemp/>

-   Endcup CRID group at SLD

-   Can come with oil contamination

-   Must recirculate and have a reasonably tight vessel

-   Use simple distillation

-   HERA-B RICH

-   Filled with C4F10 and operates at room temperature

-   HERMES @ DESY

-   C4F10 RICH for one radiator and silica aerogel tiles for the other

-   Gas control system recirculates the radiator gas through the main
    volume at a slight over pressure.