THE FAST X-RAY MONITOR (FXM)

BASED ON YAP:CE SCINTILLATOR

(YTTRIUM ALUMINUM PEROVSKITE ACTIVATED BY CERIUM)

FOR THE “CORONAS-PHOTON” SATELLITE PROJECT

E. Fedorovykh

Astrophysics Institute at Moscow Engineering-Physics Institute, RUSSIA

Instrument FXM

Goals of experiments:

• Fast monitoring of hard X-ray Solar radiation in the energy range of

20 – 600 keV with 2 – 3 ms time resolution;

• Registration of Solar flare X-ray radiation temporal profile in 6 differential

and 2 integral energy sub-bands.

FXM block-diagram

Instrument FXM consists of:

• detection block FXM-D,

• high-voltage source

block HVS-5,

• electronic block FXM-EM.

Blocks FXM-D, HVS-5 are installed on an extendable platform.

Block FXM-EM is installed in a pressure compartment.

Detection block FXM-D

FXM-D onboard “CORONAS-PHOTON”

• Overall dimensions 366x204x122 mm,

• Weight 5 kg.

Detection block FXM-DCollimator (field of view 6°)

Scintillator YAP:Ce

Light-emitting diode board

PMT

Divider

Discriminator block

Stabilization block

Preamplifier

10mm

Ø70mm

Properties of YAP:Ce

Thickness of crystal 10 mm

YAP:Ce – yttrium aluminum perovskite with cerium, YAlO3(Ce)

YAP:Ce NaI(Tl)

Decay time, ns 27 250

Density, g/cm3 5,55 3,67

Hygroscopic no very

Relative light output

40 100

Wavelength of emission max., nm

350 415

Energy spectra of YAP:Ce

ChannelC

ount

sChannel

Cou

nts

Energy spectrum of the radioactive source Am241. The crystal thickness was 10 mm.

Energy spectrum of the radioactive source Cs137. The crystal thickness was 10 mm.

Detection block FXM-DStabilization block

The measurement channel is stabilized using precise impulses from the light source (light-emitting diode) placed in the collimator in front of the crystal. The system stabilization reaction time is 0,1 s. This system controls the PMT power supply. This helps one to avoid the influence of output characteristics at high count rate.

Discriminator block

Signals from preamplifier separated according to their amplitude into six differential channels. Two integral channel are provided too.

Channel number Energy channel, keV1 20-302 30-403 40-504 50-705 70-1306 130-6007 20-6008 >600100 ns

500 mV

Output waveform

Rise time 38 ns

Fall time 116 ns

High voltage source block HVS-5

• Overall dimensions 225x190x57 mm,

• Weight 2 kg.

Block HVS-5 is adjustable high voltage source with range from 900 V to 1900 V. Controlling is realized by external control signal 0 - 10 V, generated in the stabilization block.

Electronic block FXM-EM

Block FXM-EM realize following functions:

• low voltage supply to FXM-D and HVS-5 blocks;

• change of data acquisition time interval (temporal resolution) by means of

control code words (UKS);

• counting of events in FXM-D channels, recording to data frames and transfer

to the Scientific data acquisition and registration system (SSRNI).

Conclusion

At present FXM has passed almost all preflight tests. Flight model is under making now.

FXM Web-page:

http://iaf.mephi.ru/coronas-photon_brm.htm