Focal 3

FOCAL3 (acronym of Facility for Optical Calibration At Liège)is a cylindrical stainless steel vessel of 21m³ with an vertical axis and a diameter of 3m. Its height is 3.34 m. An auxiliary chamber is annexed to the main chamber. The purpose of this chamber is to integrate a collimator simulating the light source during thermal vacuum optical tests

Characteristic

Access flanges in the chamber

• Main chamber

For light beam access, thermal fluid transfer and electrical supply, 36 flanges are distributed over the whole chamber surface.

• Auxiliary chamber

11 flanges are distributed on the whole auxiliary chamber and are available for electrical connections and optical access.

   

Focal 3 optical bench

 

 

 

 

 

 

Two optical benches are installed respectively in the main chamber and in the auxiliary chamber.

Both benches are put on the same seismic block which is actively controlled thanks to 5 air cushions, regulated by three independent closed loop lines.

The seismic block is larger than the vacuum chamber, allowing to put the OGSE outside the chamber with the same stability.

The main chamber optical bench sizes are 3 m by 1.2m. A threaded holes network (M8 separated of 200 mm) is foreseen on the upper surface.          

The microvibration levels are 100µg RMS in the 0-400 Hz bandwidth.

Pumping system

The pumping cycle is divided into 3 steps:

• primary pumping
• turbomolecular pumping
• interseal pumping

This pumping system is designed to reach 5.10^-3 Pa after 3 hours of pumping (this value is given for an empty chamber).

Crane

The 10T clean room crane can be used to install the test set-up and the specimen on the optical bench.

Thermal system

Thermal environments inside the chamber can be simulated by means of dedicated shrouds, fed with nitrogen and/or helium.

• NITROGEN thermal system :

8 independent thermal channels allow to feed dedicated panels. The temperatures can be set in the range from 123 [K] to 353 [K] for the regulation system or 85 [K] for the liquid nitrogen system (each line is equipped with a valve which selects GN2 or LN2 mode).

It is possible to reach higher temperature than 353 [K] with additional heaters glued on the specimen or with infrared lamps installed inside the thermal tent.

The thermal regulation system is designed to avoid oscillations and temperature drift.

It warrants performances about +/-0.1 [K] in long term stability and allows complex thermal cycling tests.

• HELIUM thermal system :

The Helium thermal system is composed of lines fed by one of the Helium liquefier/refrigerator (KOCH, model 1630  or LINDE TCF 20) available at CSL. One Focal3 line can be fed with Helium.

For the cold gaseous Helium line, the temperature can be controlled from 300 [K] to 50 [K].

It should be noted that the system architecture allows to feed the lines with warm Helium up to 353 [K].

• Nitrogen and helium connection :

The fluid connection for piping is SS-8-VCR Cajon type.

Data Handling

The data acquisition of Focal 3 is organized with  Keithley 2701 data loggers with industrial PC’s.

The current sensor capacity is 90 thermocouples (2 wires) or 45 PT100 (4 wires) but the number can be adapted.

The here below type of sensors are usable and readable

 

Some display screens are available in the command rooms and in the customer areas. Temperatures, gradients, alarms and warnings can be recorded and plotted.

CSL provides various communication means between the data handling system and the customer:

• The customer can be connected to the Facilities Ethernet network or have a connection to his home base through the public Internet, or through a dedicated ISDN link.
• "Teletesting",i.e the real time monitoring and control of an instrument by a customer remote data logger, can also be implemented.

Clean room and cleanliness aspects

 

 

 

 

 

The Focal 3 vacuum chamber is located in a class 10 000 (ISO 7) clean room (following US standard:FED-STD-209E).To satisfy specific requirements, a class 100 ( ISO 5)has been built around Focal 3. Movable parts allow to use the clean room 10T crane.