RADiation Effects Facility overview

The RADEF comprises two different irradiation stations, which are presented along with electron accelerator (LINAC) and control barrack in Fig. 1. One beam line is dedicated to proton irradiation in air, while the other one is meant for low-energy proton irradiation in vacuum, as well as heavy-ion irradiation both in air and in vacuum.

Fig. 1. A layout from the RADEF beam lines with LINAC cave and control barrack.

Tentative beam tuning is made to the fluorescent aluminum oxide beam viewer placed 45º with respect to the beam axis. The viewer can be moved in and out of the beam and the shape of the beam in the viewer is visualized through a glass window by a CCD camera.

For measuring the beam flux and uniformity, four photomultiplier tubes with BC-408 plastic scintillator material, were used on the sides of the beam aperture. The tubes are fixed to the beam collimator system and the detection area of each detector is 0.5 cm2. The beam purity is checked with the energy spectrum. This is especially important while using beam cocktails.

Wobbler magnets are used to achieve good beam homogeneity. The proper sweeping area is attained with the adjustable coil-currents in the wobblers.

At the end of the main beam line is a vacuum chamber with an inside diameter of 75 cm and a height of 81 cm. It allowes a vacuum environment for irradiation tests and minimise the spread in particle energy especially for low-energy proton tests. Therefore low-energy proton tests are recommended to carried out in vacuum, while heavy-ion tests can be carried out in vacuum or in air. A layout of the chamber, along with beam diagnostic equipment and collimators, is shown in Fig. 2.

Fig. 2. Heavy ion irradiation chamber and beam diagnostic equipment.

The vacuum inside the chamber is achieved after 5 minutes of pumping, and degassing takes only a few minutes. A photo from the chamber, when it is opened and ready for testing in air mode is shown in Fig. 3.

Fig. 3. RADEF chamber when opened and ready for component testing in air.

The minimum recommended cable lengths inside the vacuum chamber is 70 cm. A table for test setup control electronics can be brought right next to the vacuum chamber, so that cable lengths from vacuum chamber to the electronics are as short as possible (min recommended 70 cm).

In air mode irradiation minimum cable length from DUT setup to control electronics next of the open chamber is about 80 cm.

Shorter cables lengths are also possible if needed, but in these cases is better to do some preplanning with RADEF stuff.

Minimum cable lengths from vacuum chamber to control barrack is 10 m.

The vacuum chamber is equipped with a remotely-operated device-holding platform (a linear movement apparatus, LMA) that can be used to move the DUT in front of the beam. A beam collimator can be used to restrict the irradiation area on the device up to 8 cm of diameter (vacuum mode) (see Fig. 2), but normally beam sizes up to 2x2 cmxcm are used. In air mode, the regularly used maximum beam window size is 30 mm of diameter, but also 45 mm of diameter beam window is available for special cases.

The DUT can be moved along the horizontal and vertical axes and tilted around the vertical axis with the LMA (left in Fig. 4). The test PCB board can be fixed with spacer screws on at least 25 x 25 cm² size aluminum plate which will be mounted on the LMA. Couples of examples about the plates used for PCB board mounting are shown on the right in Fig. 4.  A detailed drawing from the plate can be found in RADEF web pages and provided upon request to the customers.

Fig. 4. A schematic picture from the LMA and couples of examples about aluminum plates with spacer screws available at RADEF can be used to mount PCB test board to the LMA.

Beam monitoring and control

Beam monitoring and control is carried out in a separate room for safety reasons. During test runs, beam flux and fluence are measured and presented on-line; information about the beam (ion, energy, LET and range in silicon) and a history of performed runs is displayed to the user on a big screen. The user can start and stop runs and change the DUT on his own. This can be done with a keyboard and a mouse. The change of ion species and tuning of the flux have to be carried out by a RADEF operator, who remains at all times at the disposition of the user. A log file regarding target device, ion species, flux, fluence, exposure time, collimator size and tilt angle is provided to the customer at the end of the test campaign. Sample displays of the screen are shown in Fig. 5 and 6.

Fig. 5. Beam monitoring and control interface.
Fig. 6. Beam aim and collimation control interface

There are a few digital I/O lines that customers can use to interact with the beam monitoring system. Flux information can be provided for customer as +5V TTL pulses: the frequency of the signal corresponds to the average flux over the previous second. Also real-time flux information is available. It is also possible to start and stop the beam and run by external TTL signal for example from customer’s data collection system. Run starts at the rising edge and stops at the falling edge. The channel works both as a sinking and sourcing input.

Customer can also use the facility's beam shutter to pause the beam during the run. This can be useful, if the test system must be power cycled after a certain error and the user wants to have the beam off while the system recovers, for example. Beam shutter can be controlled with +5 V signal. Beam is on when the signal is 0 V and the beam is stopped when signal is +5 V. It is advised that the user should be able to switch on and off the beam pause signal also manually for beam tuning and testing purposes. A logic inverting unit is also available at RADEF (0 V in = +5 V to beam shutter, +5 V in = 0V to beam shutter).

RADEF keeps some basic test equipment at the disposition of its customers. Readily available are five power supply units:

  • Delta Elektronika  (0-300V, 150W)
  • P dual-output power supply (2x 0-30V DC, 90W),
  • PS25025T (same device as PS23023DL, with an additional fixed +5V output)
  •  dual output power supply (2x 0-20V DC, 50W; GPIB and RS-232 control inputs),
  •  (combines a power supply, true current source, 6-1/2 digit multimeter, arbitrary waveform generator, V or I pulse generator with measurement, electronic load, and trigger controller – all in one instrument)
  •  (1100V, 1A, 20W)
  • a  digital oscilloscope (1GHz analog bandwidth, 5GS/s)
  • Additional equipment can be procured from other research teams at JYFL if necessary; please do not hesitate to make enquiries.

The RADEF facility floor plan
 

Contact information:
Email: heikki.i.kettunen@jyu.fi

More information

RADiation Effects Facility

RADEF, RADiation Effects Facility, is specialized in applied research related to nuclear and accelerator ­based technologies, to study of radiation effects in electronics and related materials.

Heavy-ion cocktails available at RADEF

RADEF specialty is high penetration heavy ion cocktail beams which are used for commercial services and academic research. The beams are called ion cocktails, because they are mixture of ions with almost the same mass to charge ratio.

Linear electron accelerator

The RADEF linear electron accelerator is a recommissioned Varian Clinac® medical accelerator. It is located in its own enclosure within the RADEF cave.

Proton beams at RADEF

Main characteristics of energy proton beams at RADEF.