Following on from work done on a radiation resistant power supply for
emergency lights, a new
design has been developed to cope with the higher power demands of
conventional lighting in radioactive environments.
The LED luminaire is designed to be equivalent to the 58W T8 fluorescent
tube with the following performance objectives:
Smaller physical size than an equivalent T8 luminaire to facilitate
Equivalent or higher light output (>2500lm)
CRI >= 72
Lamp Life > 50,000 hours to 50%
Sample luminaire installed in the CERN PS accelerator tunnel, April 2019.
The development of radiation hard lighting for the CERN accelerator
complex started in 2009 with some initial tests on emergency luminaires.
Since then the growing trend towards LED and the increasing emphasis on
energy efficiency in EU directives has accelerated the obsolescence of
conventional T8 fluorescent luminaires with wirewound ballasts (which,
by virtue of the lack of electronic components are intrinsically very
radiation hard). As a result CERN has been developing modifications to
conventional LED luminaire designs which allow operation in the
radioactive environment found in the accelerator tunnels.
More recent testing of optical materials, SiC diodes and GaN transistors
is awaiting publication in the RADECS proceedings 2018.
A detailed presentation of the radiation tests conducted on the GaN transistors used
as a basis for the design, and a description of the development of the operating principles of the
device is also pending journal publication.
Test data from online testing (supply energised during irradiation) is still ongoing. The circuit below shows the variation used for the online tests, where a valley fill circuit has been added to reduce harmonics from the power supply.
Functional specifications for electronic components
High Radiation areas - Linear Power Supply Module for LED lighting
Input Voltage: 230V AC RMS, between phase and neutral
Single-phase bridge rectifier topology
Output voltage: 320V DC
4x SiC (silicon carbide) Schottky diodes ST STPSC10H12G-TR
Maximum blocking voltage: 1200 V
Diodes radiation tested in IRRAD, up to 2×10^14 p/cm2.
2x GaN Gate Injection Transistors (Panasonic PGA26E019BA /
GaN Gate Injection Transistors irradiation results (IRRAD) to be
LED string current is controlled below 400mA
Voltage Tolerance: +/-10%
Input Frequency: 50Hz
Frequency Tolerance: +/- 0.5Hz
Maximum electrical power: 65 W (measured at input terminals)
Earthing Regime: TN
Filters to be implemented in production versions on both AC and DC sides
Relevant standards to be observed: IEC 61000-3-2, EN 55015, EN
50082-1, EN 50082-2 (to be applied by manufacturer)
LED module (1 unit per luminaire)
100x LED Osram Oslon Square GW CSSRM2.PM connected in series
Average DC current in our luminaire (~100 mA)
Typical voltage drop on LED at 100 mA: 2.7 V
Luminous flux (per LED) at 100 mA: ~50 lm
Luminous flux (per board) at 100 mA: ~5000 lm
Tested against radiation in IRRAD, up to 2×10^14 p/cm2.
50% reduction in light output: ~10 kGy (expected >10 year lifetime in typical CERN SPS
The design specifically excludes a transformer in order to minimise
activation of the luminaire, however significant line filtering (inductors)
should be added to the design in order to meet local EMC standards (IEC etc.).
Spice simulations are provided for the electronics model.
General specifications for the luminaire construction
The design files are in LTSpice format, including the schematic and
simulated electrical performance. You will need
to open the individual designs, and in some cases additional component
libraries from the component manufacturers will be required.