AXAS-A - Ketek

Transcription

AXAS-A - Ketek

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KETEK GmbH
Hofer Str. 3
81737 München
Phone +49-89-673467-70
Fax +49-89-673467-77
KETEK GmbH
AXAS-A
Analytical X-Ray Acquisition System –
Analogue
.
.
.
.
User’s Manual
.
.
.
.
.
.
Steffen Pahlke
Rev. 0
Information furnished by KETEK is believed to be accurate and reliable.
However, no responsibility is assumed by KETEK for its use, nor for any
infringements of patents or other rights of third parties that may result from its
use. Specifications given in this document subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights
of KETEK. Trademarks and registered trademarks are the property of their
respective owners.
KETEK GmbH, Hofer Str. 3, D-81737 München, Germany
Tel: +49-(0)89-67346770
Fax: +49-(0)89-67346777
www.ketek.net
©2012 KETEK GmbH. All rights reserved.
KETEK AXAS-A Manual
1. Table of Contents
1. Table of Contents ................................................................................................ 3
2. Revision History .................................................................................................. 3
3. Features .............................................................................................................. 5
4. Applications ......................................................................................................... 5
5. Connection Block Diagram .................................................................................. 5
6. General Description............................................................................................. 5
7. Safety .................................................................................................................. 6
8. General Restrictions and Recommendations ...................................................... 7
9. Specifications ...................................................................................................... 9
10.
Absolute Maximum Ratings ............................................................................. 9
11.
Ambient Conditions.......................................................................................... 9
12.
ESD Caution .................................................................................................... 9
13.
Pin Configuration and Functional Descriptions .............................................. 10
14.
Typical Performance Characteristics ............................................................. 11
15.
Theory of Operation ....................................................................................... 13
16.
Application and Operation Information........................................................... 15
16.1.
Pulser Input ................................................................................................ 15
16.2.
Shaper Output ............................................................................................ 15
16.3.
Preamplifier Output .................................................................................... 16
16.4.
Operating Voltages..................................................................................... 17
16.5.
Peltier Characteristics ................................................................................ 19
17.
Collimator....................................................................................................... 21
18.
Outline Dimensions........................................................................................ 22
19.
Footprint of SDDs .......................................................................................... 24
20.
Ordering Guide .............................................................................................. 25
21.
Optional ......................................................................................................... 25
22.
Contact .......................................................................................................... 26
2. Revision History
12/05 – Revision 0: Initial Version
Rev. 0
Page 3 of 26
KETEK GmbH
KETEK AXAS-A Manual
Rev. 0
Page 4 of 26
KETEK GmbH
KETEK AXAS-A Manual
3. Features
•
Analytical X-Ray Acquisition System including
Power Supplies
Regulators
Preamplifier
Filtering and adjustable voltage dividers
•
Silicon Drift Detector System
•
energy resolution down to 127eV FWHM at Mn-Kα
•
excellent peak-to-background
•
operable at an ambient temperature of up to +50°C with excellent performance
•
high count rate capability up to 1,000,000 cps
•
efficient integrated Peltier element
•
no liquid nitrogen cooling required
•
radiation hardness during more than 10 years standard count rate exposure
•
easy to use
•
active areas from 7 to 50mm² available
4. Applications
•
XRF
•
µ-XRF
•
EDX
•
EDS
•
TXRF
•
XRD
•
Handheld
5. Connection Block Diagram
Fig. 1: KETEK AXAS-A Connection Block Diagram
6. General Description
KETEK AXAS-A is the state-of-the-art X-ray detector system based on KETEK VITUS Silicon Drift
Detectors. They are used in applications such as EDX, EDS, XRF, TXRF. Due to their wide operating
temperature range they are especially suited for industrial and automotive applications. The highly
integrated design including all power supplies is providing a fully functional easy to operate system.
Rev. 0
Page 5 of 26
KETEK GmbH
KETEK VITUS SDD Manual
7. Safety
It is strongly recommended to read this user manual carefully and completely before installing or
activating the SDD. Please keep this user manual always with the system for that any operator can get
this important information. In case of resale – even when second hand – or in case of scrapping at the
end of lifetime this manual has to be given along with the system. Please handle the attached
documents “Beryllium Material Data Sheet” and “Statement of contamination…” the same way.
WARNING!
The detector contains a thin, fragile Be window. If this window is damaged, the detector
will be destroyed and cannot be repaired.
Be windows damaged due to improper handling are not covered under warranty.
This product uses – a very small amount - of toxic beryllium material at the inner side of
the detector foil. Beryllium is preferred as an entrance window coating because it
provides a light-tight seal and, further, does not introduce spurious peaks in the
measured spectrum. In normal operation there is no danger to get in contact with any
toxic materials. If the SDD window was destroyed by accident, follow our safety
instructions.
Scrapping at end of lifetime has to be done according to the (local) legal requirements.
Make the “Beryllium Material Data Sheet” available to your waste disposal contractor. Do
not scrap the SDD to your domestic waste.
Due to the very thin window foil you should take care neither to touch it with fingers nor
to bring other things or materials under test too near to it.
Keep away excessive dust particle streams from the SDD window.
Excessive electrostatic discharge might destroy the window. Take care ESD is well bled
off in your application.
Some of the SDD types are evacuated. A damaged entrance window may implode
scattering small beryllium particles in the immediate vicinity of the SDD. In this case,
rigorously clean the SDD and its surrounding area following all the precautions
mentioned in the “Beryllium Material Safety Data Sheet”.
Always keep the SDD protection cap with the system, even if fixed mounted. It’s
necessary for cleaning, service and shipping to be able to protect the beryllium window.
CAUTION!
High voltages need to be applied to the detector for use. To prevent electrical shock, do
not touch the detector.
Do not drop or cause mechanical shock to the detector. Components inside the detector
are mechanically fragile and may be damaged if the unit is dropped.
Avoid temperature shocks. If the detector is out of allowed temperature range, make
sure to acclimate slowly.
Avoid air pressure shocks. Especially in evacuated applications take care to ventilate
slowly.
Let the protection cap be mounted at the SDD as long as the system isn’t mounted in its
end application. Your end application has to be designed that way to make unexpected,
damaging contact with the SDD window impossible. Make sure your samples under test
might never touch the SDD window.
Do not remove the protective cap from the detector until data is to be taken. The detector
window is made from thin beryllium which is extremely brittle and can shatter very easily.
Do not have any object come in contact with the window. Do not touch the detector
because the oil from the fingers will cause it to oxidize. Use gloves. The window cannot
be repaired. If the window is damaged the detector assembly must be replaced. Be
windows damaged due to improper handling will not be covered under warranty. Keep
the protective cover nearby at all times and cover the detector when the instrument is not
in use.
Rev. 1
Page 6 of 26
KETEK GmbH
Radiation damage to the detector will occur if it is exposed to a high flux environment.
Synchrotron Radiation Beams should be modified with attenuators before they are
allowed to strike the detector or the fluorescence target. Damage to the detector will be
permanent if the flux from an X-Ray Tube, a strong nuclear radiation source, or an
accelerator is not attenuated.
No user serviceable parts inside the units. Refer servicing to KETEK GmbH. To prevent
electrical shock, do not remove covers.
Keep the device dry and clean!
Warranty
KETEK GmbH warrants to the original purchaser this instrument to be free from defects in materials
and workmanship for a period of one year from shipment. KETEK GmbH will, without charge, repair or
replace (at its option) a defective instrument upon return to the factory. This warranty does not apply in
the event of misuse or abuse of the instrument or unauthorized alterations or repair. KETEK GmbH
shall not be liable for any consequential damages, including without limitation, damages resulting from
the loss of use due to failure of this instrument. All products returned under the warranty must be
shipped prepaid to the factory with documentation describing the problem and the circumstances
under which it was observed. Additionally the statement of contamination must be filled out completely
and returned with the product. KETEK must be notified prior to return shipment. The instrument will be
evaluated, repaired or replaced, and promptly returned if the warranty claims are substantiated. A
nominal fee will be charged for unsubstantiated claims. Please include the model and serial number in
all correspondence with KETEK.
Care Instructions
Do not clean the System under any circumstances. Do not use any alcoholic, acid or rubbing cleaning
agents.
8. General Restrictions and Recommendations
Rev. 1
-
avoid touching the entrance window of the detector module. It contains hazardous materials
-
Do not open the system
Page 7 of 26
KETEK GmbH
Rev. 1
Page 8 of 26
KETEK GmbH
9. Specifications
Parameter
VOLTAGES
positive
negative
CURRENTS
positive
negative
WEIGHT
Conditions/Comments
Min
Typ
Max
Tolerance
+11
-11
+12
-12
+13
-13
±1
±1
50
20
250
50
690
350
150
100mm Finger Length
Unit
V
V
mA
mA
g
These specifications refer to the whole VITUS SDD class. Please refer to the individual SDD
datasheet for detailed information.
10. Absolute Maximum Ratings
Parameter
VOLTAGES
positive
negative
CURRENTS
positive
negative
Radiation Hardness @17keV
Stresses beyond those listed under Absolute
Rating
Maximum Ratings may cause permanent
+18VDC
-18VDC
damage to the device. This is a stress rating
500mA fused
250mA fused
12
≤ 10 Photons
or any other conditions above those indicated
only; functional operation of the device at these
in the applications and operations section of
this specification is not implied. Exposure to
absolute
maximum
rating
conditions
for
extended periods may affect device reliability.
11. Ambient Conditions
Parameter
OPERATING
Temperature
Humidity
Pressure
Pressure Change
STORAGE
Temperature
Humidity
Min
Max
Unit
0
10
0
60
80
1.1
100
°C
% RH
atm
mbar/s
0
10
60
90
°C
% RH
Conditions
non condensing
non condensing
12. ESD Caution
ESD (Electrostatic Discharge) sensitive device.
Charged devices and circuit boards can discharge without
detection. Although this product features patented or proprietary
protection circuitry, damage may occur on devices subjected to
high energy ESD. Therefore, proper ESD precautions should be
taken to avoid performance degradation or loss of functionality.
Rev. 1
Page 9 of 26
KETEK GmbH
13. Pin Configuration and Functional Descriptions
*AXAS-A HD-15 connector
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Description
Mnemonic
GND
GND
Input Voltage positive
Input Voltage negative
+12V
GND
GND
GND
-12V
Temperature Output
TempMon
Preamplifier
Output
Test Pulse
Input
Temperature
Output
LED
Power
Indicator
HD-15
Power Connector *
Rev. 1
Page 10 of 26
KETEK GmbH
14. Typical Performance Characteristics
Fig. 2: Typical KETEK VITUS Silicon Drift Detector Spectrum of H7 active area type SDD with an Fe-55 source,
taken with an KETEK preamplifier and an analogue shaping amplifier.
1.0
0.9
0.8
Transmission
0.7
0.6
8 µm
12.5 µm
25 µm
0.5
0.4
0.3
0.2
0.1
0.0
500
1000
1500
2000
2500
3000
Photon energy (eV)
Fig. 3: Typical transmission of KETEK Silicon Drift Detectors with different Beryllium entrance window thickness
Fig. 4: Typical transmission of KETEK Silicon Drift Detectors with low energy AP3.3 entrance window
Rev. 1
Page 11 of 26
KETEK GmbH
Chip Temperature (°C)
Fig. 5: Typical absorption efficiency of KETEK Silicon Drift Detectors with a thickness of 450µm and 8µm Beryllium window
-40
stable -40°C chip temperature possible
up to +50°C ambient
-45
stable -45°C chip temperature possible
up to +40°C ambient
-50
-55
co
an
nst
ll
t fu
Pe
w
r po
l ti e
er
-60
20
25
30
35
40
45
50
Ambient Temperature (°C)
Fig. 6: Typical control range of Silicon Drift Detector chip temperature at different ambient temperatures
Fig. 7: Typical calculated energy resolutions of Silicon Drift Detectors for low energies
Rev. 1
Page 12 of 26
KETEK GmbH
15. Theory of Operation
The silicon bulk of the Silicon Drift Detector (SDD) has to be depleted completely to make the sensor
sensitive for incoming photons. By applying a negative voltage to the back contact of the SDD, the
detector bulk is completely depleted. An incoming photon will generate a number of electrons and
holes dependent on its energy. The holes drift to the back side of the detector formed by the large
area back contact whereas the electrons drift to the anode where the accumulated charge can be
measured or read out. The drift field for the electrons is applied by a ring structure on one side of the
SDD with a negative voltage at the outer ring (Ring X) and a voltage close to 0V at the innermost ring
(Ring 1).
Fig. 8: Silicon Drift Detector potential diagram
The anode is connected to: a) the gate of the first field effect transistor (FET), b) the feedback
capacitance (CFB) and c) the cathode of the reset diode (DRES). The combination of a) and b), the FET
and the feedback capacitance, respectively, forms the first part of a charge sensitive amplifier, used to
read out the accumulated electrical charge. The combination forms a transimpedance (current to
voltage) and an integrator when connected to the subsequent stages of the pre-amplifier. Therefore
the source of the FET has to be connected to ground and the drain voltage and current need to be set
appropriately (typically 3V and 3mA). The operating point of the FET is optimized by setting its bulk or
substrate voltage.
GND
UOR
Driftfield
UIR
Anode
-V
UBACK
Homogeneous thin entrance window
Fig. 9: Silicon Drift Detector schematic
Rev. 1
Page 13 of 26
KETEK GmbH
The FET is operated in a common source configuration. The leakage current sensed at the FET gate
causes a ramp signal at the output of the pre-amplifier. The slope of the ramp signal, and thus its
frequency, is dependant on the operating temperature. The incoming photons generate short current
pulses, with a certain rise time (dependant on the location of interaction of the x-ray with the SDD
chip), and a certain duration and amplitude (dependent on the energy of the incoming photon). In turn,
these short pulses generate steps superimposed on the pre-amplifier’s ramped output signal. The
height of a step contains the information necessary to determine the energy of the interacting photon.
1,5
Preamp Out
Reset Out
1
Amplitude [V]
0,5
0
-0,5
-1
-1,5
0
5
10
15
20
Time [ms]
Fig. 10: Typical KETEK Preamplifier Output Signal including Preamplifier Reset Pulse Output
using a KETEK VITUS SDD irradiated with an Fe-55 Source at -35°C Operating Temperature
0,04
0
Amplitude [V]
-0,04
-0,08
Preamp
Out
-0,12
-0,16
0
20
40
60
80
100
120
Time [µs]
Fig. 11: Zoom of Figure 13, typical KETEK Preamplifier Output Signal including Preamplifier Reset Pulse Output
using a KETEK VITUS SDD irradiated with an Fe-55 Source at -35°C Operating Temperature showing step like pulses
Rev. 1
Page 14 of 26
KETEK GmbH
16. Application and Operation Information
For (optimal) operation, SDDs require the application of several voltages and integration with a charge
sensitive amplifier and other pulse forming electronics (either analog or digital). Typically, a high
voltage DC power supply feeds the drift ring voltages; a high current, linearly regulated, low voltage
power supply feeds the Peltier element; and a bipolar, linearly regulated power supply feeds the
charge sensitive amplifier and pulse forming electronics.
The drift ring voltages can be generated from a filtered high voltage rail, by using several voltage
dividers. Each detector may have individual ring currents. Thus potentiometers should be used for
voltage adjustments as the voltage drop at the voltage dividers depends on the ring currents.
Fig. 12: KETEK Silicon Drift Detector connected to typical preamplifier board – block diagram
The Peltier power supply should be regulated with a PI/PID loop to keep the operating temperature of
the SDD chip stable. Therefore it is necessary to read out the temperature sensor of the SDD.
16.1.
Pulser Input
The BNC connection gives the possibility to connect an external spectroscopic pulser (e.g. ORTEC
419). The pulser output should be negative pulses with maximum amplitude of 10V. The risetime
should be in the range of 20 to 200ns with a falltime of a few µs.
16.2.
Shaper Output
Disabled. Not available any more.
Rev. 1
Page 15 of 26
KETEK GmbH
16.3.
Preamplifier Output
For the design of the preamplifier the FET is used in the common source configuration. Therefore the
source of the FET can be connected directly to signal ground. The drain drives the signal. The
substrate or bulk should be adjusted to the value given in the datasheet of each single SDD. Also a
low pass filter should be used to suppress any noise. Typical values are:
Substrate/Bulk: RSUB = 10kΩ,
CSUB = 4.7µF/16V Tantalum, low ESR
The drain is driven by a simple current source formed by a resistor. Additional low pass filtering is
mandatory. Tantalum capacitor with low ESR of at least 100µF should be chosen.
The Drain and Feedback lines should be well separated to avoid any ringing or crosstalk. The
Substrate voltage can be adjusted by a potentiometer.
The Reset circuit includes a current limiter. This will protect the sensitive reset diode mechanism
inside the SDD.
Fig. 13: Preamplifier connection block diagram
There are two options for the preamplifier output which can be chosen by the customer:
a) Ramped / Reset Type Output Signal:
See figure above. The output shows a ramped output signal with a range of ±4V maximum and step
like pulses for each single photon. These steps have typical amplitude of 5mV/keV. Other gains on
request.
b) Exponential Decayed / RC Feedback Type Output Signal:
An additional analogue filtering is used right after the Ramped or Reset Type Preamplifier. This filter
consists of a RC High Pass Filter, shaping the pulse to an exponential decayed signal. The typical
decay time is 6 to 200µs, others on request. An additional gain is provided so the amplitude of each
single pulse is typically 10mV/keV. The output signal has a negative polarity.
Rev. 1
Page 16 of 26
KETEK GmbH
Fig. 14: KETEK AXAS-A exponential decay preamplifier signal output
16.4.
Operating Voltages
Several voltages are needed for operating the detector (exact values are given in each detector data
sheet), for example:
1.
Ring 1
= approx. -20V
2.
Ring X
= approx. -130V
3.
Back
= approx. -65V
The detector voltages should be filtered using the following combinations of resistors and capacitors
providing low pass filters:
Rev. 1
1.
Ring 1:
RR1 = 15kΩ,
CR1 = 220nF
2.
Ring X:
RRX = 500kΩ,
CRX = 47nF/250V
3.
Back:
RBack = 1MΩ,
CBack = 47nF/250V
Page 17 of 26
KETEK GmbH
Fig. 15: Operating voltages filtering block diagram
In case of AXAS-A these filters are included. Additionally there are three potentiometers available to
adjust the three necessary SDD voltages (R1, RX and Back) to the appropriate voltages necessary for
each single SDD.
Before switching on the system, the output-signal of the preamplifier and the shaped signal should be
connected to an oscilloscope.
The preamplifier operating voltage must be switched on first.
The detector voltages should be switched on in the following order:
R1 – RX – Back
The voltages to be applied must be set according to the detector datasheet. Typical currents flowing
are several µA through Ring 1 and Ring X (voltage divider) and approx. 1nA for the back contact if the
back voltage is applied. R1 and RX currents should be equal!
After switching on the detector voltages the signal of the preamplifier should show a ramp. The ramp
period depends on the chip temperature. At -35°C the ramp period should be in the range of several
microseconds.
Rev. 1
Page 18 of 26
KETEK GmbH
16.5.
Peltier Characteristics
The KETEK Silicon Drift Detectors are provided in three different performance grades, based on the
package’s internal atmosphere and size: evacuated TO-8 packages (H7, H20, H30, and H50);
evacuated non-TO-8 packages for larger devices (H80, R100); and, low-energy, nitrogen filled TO-8
packages (H7-LE, H15-LE). The three types have different cooling capabilities because of the
different internal atmosphere (vacuum or nitrogen) and different sizes.
4
H7-LE
3
H80
Power [W]
H7
2
1
0
-60
-50
-40
-30
-20
-10
0
10
20
Temperature [°C]
Fig. 16: Typical power consumption of the three different KETEK VITUS SDDs
It is strongly recommended to limit the current as mentioned in chapter “10. Absolute Maximum
Ratings”. Stresses above those listed under “Absolute Maximum Ratings” may cause permanent
damage to the device. Functional operation of the device at these or any other conditions above those
indicated in the applications and operations section of this specification is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Please note that the behaviour of the Peltiers can vary with changed ambient temperatures. The
efficiency of the Peltier elements is increasing approximately by 0.5K for each Kelvin of increasing
ambient temperature. Additionally the step response factor will change which will influence the
parameters of the control loop for the regulation of the operating temperature.
Rev. 1
Page 19 of 26
KETEK GmbH
20
10
0
100mA
Temperature [°C]
-10
-20
200mA
-30
300mA
-40
400mA
-50
500mA
700mA
-60
0
50
100
150
200
250
300
350
400
Time [s]
Fig. 17: Typical H7 step response functions for different Peltier currents
using a diode as temperature sensor with 1µA operating current and 10V compliance voltage.
20
10
100mA
0
Temperature [°C]
200mA
-10
300mA
-20
400mA
500mA
-30
600mA
700mA
-40
800mA
900mA
-50
1000mA
-60
0
50
100
150
200
250
300
350
400
Time [s]
Fig. 18: Typical H80 step response functions for different Peltier currents
20
100mA
Temperature [°C]
0
200mA
300mA
400mA
-20
500mA
600mA
700mA
900mA
-40
-60
0
50
100
150
200
250
300
350
400
Time [s]
Fig. 19: Typical H7-LE step response functions for different Peltier currents
Rev. 1
Page 20 of 26
KETEK GmbH
17. Collimator
The KETEK Multilayer Collimator consists of a Tantalum (Ta) foil covered with stacked layers of
Chromium (Cr), Titanium (Ti) and Aluminium (Al). The purity of the layers is ≥99%.
All collimators are mounted on-chip.
Optionally, KETEK offers an external outer clip-on collimator VPROTECT. Depending on the
application, the geometry of the x-ray beam can differ. To avoid any foreign absorption or fluorescence
the additional collimator can optimize the beam geometry.
Fig. 20: KETEK additional external clip-on collimator
Rev. 1
Page 21 of 26
KETEK GmbH
18. Outline Dimensions
Rev. 1
Page 22 of 26
KETEK GmbH
H7LE
H15LE
Ø
H7
H20
H30
H50
H80
R100
Fig. 25: Outline dimensions of the different KETEK VITUS Silicon Drift Detector types
Rev. 1
Page 23 of 26
KETEK GmbH
19. Footprint of SDDs
For H7, H20, H30, H50 SDDs: (Bottom View), M4x6 Screw
Mating connectors:
-
Type Tyco Electronics/AMP 6-5330808-5
For H80 and R100 SDDs: (Bottom View), M6x8 Screw
Mating connectors:
Rev. 1
-
-
Page 24 of 26
KETEK GmbH
20. Ordering Guide
Encapsulation
Window
Cap
material
Collimator
-
Active area
-
window
Chip entrance
O
Temp. Sensor
2
Peltier
T
FET
5
450µm
Product AXAS
Chip thickness
A
Example:
A5T2T0-H30-ML8BEV: VITUS AXAS-A 450µm SDD Chip with Thermistor as temperature sensor,
active area of 30mm² with high peak-to-background ratio, multilayer collimator in a bevelled cap with a
Be window sealed under vacuum.
21. Optional
Optional available are different KETEK products in combination with the VITUS Silicon Drift Detector:
-
KETEK Preamplifier: High performance stand-alone preamplifier for SDD applications
-
KETEK VIAMP: VITUS SDD in combination with preamplifier
-
KETEK AXAS-D: Analytical X-ray Acquisition System - DIGITAL
-
KETEK VPROTECT: external collimator
For detailed information please contact KETEK Sales and Marketing Office.
Rev. 1
Page 25 of 26
KETEK GmbH
22. Contact
KETEK Headquarter Sales Office
KETEK GmbH
Hofer Str. 3
81737 München
Email
[email protected]
Phone +49 (0) 89 673467 70
Fax
+49 (0) 89 673467 77
www.ketek.net
Rev. 1
Page 26 of 26
KETEK GmbH

AXAS-A - Ketek

Transcription

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