UVES exp. meter system

The UVES exp. meter system will do everything you requested above, except automatically peaking up a signal (for autoguiding). Since UVES has slit viewers, we don't need this. The system has following predicted performance on an 8 m UT (Nasmyth):

m=18, B: 70 cps (dark: 4 cps @ 25 deg)

m=18, V: 50 cps (dark: 35 cps @ 25 deg)

I think the best is for you to copy the hard - and software of the UVES exp.meters. This would be the least of work for you. Main elements are:

- The optical pickup system of the exp. meters which should probably be tailored to your application. In UVES we pick up 2.5% of the light coming through the slit with a strip mirror that is located just before the echelle.

- The beam size is 200 mm at this location and the mirror is 4 mm wide by 200 long, in front of the gap in the echelle mosaic so we don't lose light.

- The strip mirror is a diamond machined Al parabola with an F of 70 cm. It makes a 3x reduced, 2 mm image of our 6 mm long slit (15 arcsec) on the input end of a 1.5 m, 2 mm dia. liquid fiber (Lumatec Liquid Lightguide 300 or 380, the -300 type has good UV transmission).

- The fiber goes to a photon counting PMT where it ends just before the cathode. Pickup system: ~ 5000 DM.

-PMT's. These are Hamamatsu Side-on Photon Counting heads, H6240 Series, ~ DM 5000/Pc. They are self-contained and require only a 5V DC, 100 mA supply voltage. The provide TTL output pulses, one for every photon counted. Max. count rate is 2.5 Mcps (10% linearity). Dimensions: 35 x 50 x 95 mm.

Optical data:

Blue: model H6240, selected for dark counts < 10 cps at 25 deg C and QE 15% at 300 nm. Actual values are 4 cps and 20%, respectively.

Red: model H6240-1, selected for dark counts < 50 cps at 25 deg C and QE 16% at 400 nm and > 11% at 600 nm. Actual values are 35 cps, 20% and 11%, respectively.

Counter: HP53132A programmable laboratory counter with HP-IB interface. It can be programmed manually and from the ICS. In UVES the integration time is set to 1 sec.

~ DM 3000.

HP-IB to VME interface: National Instruments type GPIB-232CT-A. ~ DM 600

Shutter: Prontor Electronic - M size 0 (dia. 24 m) 24V DC, 0.25 W. This shutter is mounted on the input of the fiber, to measure dark current and to protect the PMT from overexposure during maintenance. ~ DM 500

Shutter controller board: ESO development. We could probably provide one or two for you, along with spares for UVES that will be ordered around Q2/99.

Software: The VLT SW has a basic LCU test routine for testing communication with the HP-IB to RS232 interface: Within the VLT SW archive, do:

>CmmCopy uvisen

>cd uvisen/test

>ls uvisenTestExpMeter.c

the file uvisenTestExpMeter.c is the one you want. If you want more, I suggest your SW engineer contacts R. Schmutzer or A. Longinotti to get the routines he needs.

GUI: the blue and red exposure meter each has a "strip-chart" panel that is refreshed once per second and shows a graph of the count rate over the past 20 minutes, the current counts and the cumulative counts since last exp. start. Possibilities exist for changing graph scale, scrolling back in time, opening and closing the shutter. GUIs are still under development

I am sending by fax some documentation sheets of the hardware and of the GUIs. Please contact me if you need more.

Regarding the I2 cell, it is still not finished (manpower problems) but we do intend to get an FTS once it is finished.

Best regards, Hans Dekker