Focal 6.5
Focal 6.5 (acronym of Facility for Optical Calibration At Liège) is a cylindrical vessel in stainless steel of 168 m3, with a vertical axis and a diameter of 6.5 m. The chamber is composed of three parts: the lower dished end, the intermediate part including access door and the cover which are movable.
Characteristics
Access flanges in the chamber
For light beam, thermal fluid transfer and electrical supply, 59 flanges are distributed over the whole chamber surface mainly distributed at the optical bench level.
Focal 6.5 optical bench
The optical bench, made of aluminium alloy of diameter 5500 mm bench is supported by 3 feet passing through the wall of the vessel and is insulated from mechanical vibrations by bellows, which also ensure vacuum. These feet stand on a seismic block. The level of vibration on the optical bench doesn't exceed 100 µg in the range from 1 Hz to 100 Hz with specimen active system.
Its upper surface is equipped with a M10 holes network [300 * 300] mm for equipment fixation.
Two manholes (700 and 500 mm diameter) are foreseen in the bench for cleanability aspects.
Additionally, some areas, mechanically decoupled from the bench, are accessible for the integration of Ground Support Equipment (thermal shroud,…)
A platform is located in the upper part of Focal 6.5 and allows to put OGSE to calibrate specimen located on the optical bench.
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 4 hours of pumping (this value is given for an empty chamber).
Crane
The 10T crane from the clean room can be used to install set-up and specimen on the Focal 6.5 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 :
10 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 comprises 1 channel fed by one of the two helium liquefier/refrigerator.
- Nitrogen and helium connection :
The fluid connection for piping is SS-8-VCR Cajon type.
Data Handling
The data acquisition of Focal 5 is organized with Keithley 2701 data loggers with industrial PC’s.
The current sensor capacity is 320 thermocouples (2 wires) or 160 PT100 (4 wires) but the number can be adapted.
The here below type of sensors are usable and readable:
| Thermocouple : T and K type | Resistance 4 wires |
| Diode 4 wires | Cryogenic diode |
| PT100 2 wires | Cernox ([Ω] or [K]) |
| PT100 4 wires | Thermistor |
| PT500 2 wires | Voltage 0-1 [V] et 0-10 [V] |
| PT1000 2 wires | Current< 100 [mA] |
| PT2000 4 wires |
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 6.5 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) of 670 m3 has been built around Focal 6.5. The Iso5 tent displacement allows to use the clean room 10T crane.
The Focal 6.5 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) of 670 m3 has been built around Focal 6.5. The Iso5 tent displacement allows to use the clean room 10T crane.
