The VIRMOS Mask Manufacturing Unit

Mask Manufacturing Unit

The VIRMOS Mask Manufacturing Unit (MMU) is one of the main contributions of IFCTR to the VIRMOS project. Its purpose is

to produce the masks for the VIMOS and NIRMOS multi-object spectrographs with characteristics corresponding to the VIRMOS specifications, in a reasonable time and in advance of the observations
to manage the intermediate storage of up to 100 mask sets (400 masks) per instrument, with automated identification
to manage the insertion of the masks in the 15 slots of the 4 Instrument Cabinets (ICs) (which are a part of the VIMOS and NIRMOS instruments supplied by OAC Naples)
to perform the above operations in response to orders received by higher level ESO/VIRMOS software
to allow a quality check of the produced masks
in addition the VIRMOS MMU will be used by ESO to support also (manually) the manufacturing of FORS2 masks.

Further information

A collection of commented pictures is available describing the activities done until July 2000 for development and testing in Milan and the installation of the MMU in Paranal recently concluded.

References

A paper (Conti et al. 1999) describing the MMU at its current status was presented in May 99 at the S.Agata SAIt international conference on "Telescopes, instruments and data processing for astronomy in the year 2000" : it is available in preprint form at astro-ph/9907322 and as final publication in PDF format in Volume 2, no. 2 of the electronic Astrotech Journal.
An account (Avila et al. 2000) of the installation of the MMU at Paranal has appeared in Dec 2000 on the ESO Messenger 102 in postscript form
A further paper (Conti et al. 2001) has been published on in April 2001 (see the abstract on ADS, or the electronic article (PASP subscribers only) or a local PDF version).
The VIRMOS MMU Operator and Maintenance Manuals are also available on line, with restricted access to members of the VIRMOS Consortium and ESO.

Executive summary

A further page gives a block diagram of the MMU configuration and a summary of the MMU principles of operation.

Performances

Roughness of slit edge at pixel size scale (0.12 mm)	W_q = 0.38 +/- 0.07 micron where W_q is the rms of the filtered roughness profile above a 0.12 mm cutoff
Waviness of slit edge (typical slit length 6-7 mm)	W_t = 1.3 +/- 0.3 micron where W_t is the maximum peak-to-valley of the profile above a 2.5 mm cutoff
Slit width	> 80 micron (limited by laser beam diameter 40 micron)
Slit length	< 20 mm (shavings larger than this size cannot be disposed of by the exhauster
Positioning accuracy	< 15 micron at the machine (allow for further 15 micron at the focal plane including thermal expansion of mask support)
Cutting speed	6 mm/sec for fine cutting (slits) 20 mm/sec for coarse cutting (contours)
Manufacturing time	from 460 s for one "empty" mask (overhead due to Invar sheet mounting, connection set-up, cutting of contour and fixed features ) to 950 s for one mask with 200 slits

sax.iasf-milano.inaf.it/~lucio/Virmos/MMU-Html/index.html :: original creation 2007 set 13 12:00:51 CEST :: last edit 2007 Sep 13 12:00:51 CEST