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Centre for Advanced Instrumentation

IMACS-IFU

The IFU in its housing. Light incidence from above. The pickoff mirrors bend the light into the fore-optics barrels. Fibers (not shown) re-arrange the
spatial elements into the single, curved slit pointing downwards. The diameter of the main frame is about 670 millimeters.

IMACS IFU inserted in the IMACS slit mask server as seen from telescope side

Introduction

IMACS IFU is an integral field unit currently being developed for Carnegie's Magellan I 6.5 m telescope at Las Campanas, Chile.  

As an optional part of IMACS (Inamori MAgellan Cassegrain Spectrograph), the IMACS IFU can be moved into the focal plane by the IMACS mask server
in the same manner like an ordinary slit mask.

Current status (06/2002):  Procurement and manufacture.

Basic Specifications

Spectrograph scales:  

f/1.49 "short" IMACS camera and f/2.67 "long" IMACS camera can be used.

(Parameters for the long camera are provided in brackets if different from short camera parameters).

Spatial setup: 2 Fields (object plus background) of 6".92 by 5".00 (4".15 by 5".00) each.
Number of apertures: 1000 (600) per field
Format: 25 by 40 (25 by 24) elements
Shape:  Rectangular pattern of hexagonal lenslets
Spatial resolution:  0".2 per microlens element
Wavelength range:  400 .. 900 nm
Spectral resolution: R < 1800 (IMACS grism mode) / 10000 (IMACS grating mode)

 

Description Of The Instrument

IMACS consists of a mask server having a capacity of 6 masks for multiobject and long slit spectroscopy. Each mask has a diameter of approximately 670 mm. The IFU will be inserted into the server similar to a standard mask. The space consumption is 3 masks slots due to its larger thickness. The IFU will consist of two fields separated by 60". Each field will have 6".92 by 5".00 or 4".15 by 5".00 depending on the spectrograph camera being used. Beam switching is possible by nodding the telescope. Both fields are re-arranged into a single 520 mm long slit, which  follows the field curvature of the spectrograph.

The 520 mm long slit of the IFU follows the curvature of the spectrograph, which normally matches the curved focal plane of the f/11 Gregorian-Nasmyth focus.Using the 8192 by 8192  IMACS CCD detector with 15 micron pixels, there will be 2.35 4.25) pixels / spectrum in cross dispersion direction with some geometric losses due to the output lenslet pitch. Along the wavelength axis the effective slit width is 4 (7.3) pixels for 99 % of the spot, or about the half for the FWHM.

Images Of Manfacture (Summer 2002)

While the fiber bundles and optics are manufactured at different companies, the in-house production of most of the mechanical parts has started. These parts are the fore-optics housings, pickoff mirror assemblies, the slit comb and the base plate which carries the whole instrument, including its interface parts to the IMACS slit mask server. Together with the input tube array, some images of the parts already finished are provided below: