ORTEC Alpha Duo Instructions for use

ORTEC
®
Alpha Duo®, Alpha Mega®,
and Alpha Ensemble®
Integrated Alpha Spectrometer
Hardware User’s Manual
Printed in U.S.A. ORTEC Part No. 932505 0520
Manual Revision F

Advanced Measurement Technology, Inc.
a/k/a/ ORTEC®, a subsidiary of AMETEK®, Inc.
WARRANTY
ORTEC®warrants that the items will be delivered free from defects in material or workmanship. ORTEC makes no other
warranties, express or implied, and specifically NO WARRANTY OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE.
ORTEC’s exclusive liability is limited to repairing or replacing at ORTEC’s option, items found by ORTEC to be defective
in workmanship or materials within one year from the date of delivery. ORTEC’s liability on any claim of any kind, including
negligence, loss, or damages arising out of, connected with, or fromthe performance or breach thereof, or from the manufacture,
sale, delivery, resale, repair, or use of any item or services covered by this agreement or purchase order, shall in no case exceed
the price allocable to the item or service furnished or any part thereof that gives rise to the claim. In the event ORTEC fails to
manufacture or deliver items called for in this agreement or purchase order, ORTEC’s exclusive liability and buyer’s exclusive
remedy shall be release of the buyer from the obligation to pay the purchase price. In no event shall ORTEC be liable for special
or consequential damages.
Quality Control
Before being approved for shipment, each ORTEC instrument must pass a stringent set of quality control tests designed to
expose any flaws in materials or workmanship. Permanent records of these tests are maintained for use in warranty repair and
as a source of statistical information for design improvements.
Repair Service
If it becomes necessary to return this instrument for repair, it is essential that Customer Services be contacted in advance of
its return so that a Return Authorization Number can be assigned to the unit. Also, ORTEC must be informed, either in writing,
by telephone [[phone]] or by facsimile transmission [[phone]], of the nature of the fault of the instrument being
returned and of the model, serial, and revision (“Rev” on rear panel) numbers. Failure to do so may cause unnecessary delays
in getting the unit repaired. The ORTEC standard procedure requires that instruments returned for repair pass the same quality
control tests that are used for new-production instruments. Instruments that are returned should be packed so that they will
withstand normal transit handling and must be shipped PREPAID via Air Parcel Post or United Parcel Service to the designated
ORTEC repair center. The address label and the package should include the Return Authorization Number assigned.
Instruments being returned that are damaged in transit due to inadequate packing will be repaired at the sender’s expense, and
it will be the sender’s responsibility to make claim with the shipper. Instruments not in warranty should follow the same
procedure and ORTEC will provide a quotation.
Damage in Transit
Shipments should be examined immediately upon receipt for evidence of external or concealed damage. The carrier making
delivery should be notified immediately of any such damage, since the carrier is normally liable for damage in shipment.
Packing materials, waybills, and other such documentation should be preserved in order to establish claims. After such
notification to the carrier, please notify ORTEC of the circumstances so that assistance can be provided in making damage
claims and in providing replacement equipment, if necessary.
Copyright © 2020, Advanced Measurement Technology, Inc. All rights reserved.
ORTEC®is a registered trademark of Advanced Measurement Technology, Inc. All other trademarks used herein are the
property of their respective owners.
NOTICE OF PROPRIETARY PROPERTY — This document and the information contained in it are the proprietary
property of AMETEK Inc., ORTEC Business Unit. It may not be copied or used in any manner nor may any of the information
in or upon it be used for any purpose without the express written consent of an authorized agent of AMETEK Inc., ORTEC
Business Unit.

TABLE OF CONTENTS
1. INTRODUCTION........................................................... 1
1.1. AboutthisManual....................................................... 3
2. INSTALLATION ........................................................... 5
2.1. Install CONNECTIONS .................................................... 5
2.2. Install MAESTRO and Other Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Connect to the PC and Input Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3.1. Multiple-Duo / -Mega / -Ensemble Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4. InstalltheDetector...................................................... 6
2.5. ConnecttotheVacuumPump ............................................. 7
3. OPERATION............................................................... 9
3.1. Controlling Chamber Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1.1. Manual.......................................................... 9
3.1.2. Automatic ....................................................... 9
3.2. Venting the Alpha Chamber(s). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2.1. Manual......................................................... 10
3.2.2. Automatic ...................................................... 10
3.3. Inserting a Sample into the Vacuum Chamber. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.4. Resolution Measurement and Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.5. MCB Properties in MAESTRO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.5.1. Amplifier....................................................... 12
3.5.2. Amplifier2 ..................................................... 13
3.5.3. ADC........................................................... 13
3.5.4. Stabilizer....................................................... 14
3.5.5. HighVoltage.................................................... 15
3.5.6. About.......................................................... 15
3.5.7. Alpha.......................................................... 16
3.5.7.1. Vacuum Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.5.7.2. Data Collection Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.5.7.3. InternalPulser............................................ 16
3.5.7.4. Alpha Chamber Data Display in AlphaVision. . . . . . . . . . . . . . . . . . . 17
3.5.8. Presets......................................................... 17
4. MAINTENANCEANDSERVICE............................................. 19
4.1. Decontamination....................................................... 19
4.1.1. Chamber Decontamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.1.2. ULTRA Detector Decontamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.1.3. Ruggedized Detector Decontamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
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ORTEC®Alpha Duo®, Alpha Mega®, Alpha Ensemble®— Hardware User’s Manual 932505F / 0520
4.2. Removing and Replacing Chambers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.2.1. ChamberRemoval................................................ 20
4.2.2. ChamberInstallation.............................................. 22
4.3. Troubleshooting ....................................................... 22
4.3.1. Can’t Find the Duo or Mega on the Detector Pick List . . . . . . . . . . . . . . . . . . . 23
4.3.2. Data or Settings Are Lost When Power Is Turned Off. . . . . . . . . . . . . . . . . . . . 23
4.3.3. ResolutionProblems.............................................. 23
4.3.4. Troubleshooting Vacuum Problems in the Alpha Ensemble . . . . . . . . . . . . . . . 24
5. SPECIFICATIONS......................................................... 27
5.1. Performance .......................................................... 27
5.2. BiasSupply........................................................... 27
5.3. CalibrationPulser...................................................... 28
5.4. DetectorCurrentMonitor................................................ 28
5.5. Preamplifier........................................................... 28
5.6. DigitalMCA.......................................................... 29
5.7. Presets............................................................... 29
5.8. VacuumChamber...................................................... 30
5.9. Indicators............................................................. 30
5.10. Controls............................................................. 30
5.11. Connectors .......................................................... 31
5.12. ElectricalandMechanical............................................... 31
5.12.1. AlphaDuoandMega ............................................ 31
5.12.2. AlphaEnsemble................................................. 31
5.13. BatteryBackup....................................................... 32
5.14. FeatureMaskBits..................................................... 32
APPENDIX A. FIRMWARE COMMANDS AND RESPONSES . . . . . . . . . . . . . . . . . . . . . . 37
A.1. CommandFormat...................................................... 37
A.2. ErrorCodes .......................................................... 37
A.2.1. Dollar Response Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
A.2.2. MCBCommands ................................................ 39
APPENDIX B. CHANGING TO AN OPPOSITE-POLARITY DETECTOR . . . . . . . . . . . . . 57
B.1. Recalibration ......................................................... 62
INDEX ..................................................................... 65
iv

CAUTION To prevent moisture inside of the instrument during external cleaning, use only
enough liquid to dampen the cloth or applicator.
Safety Instructions and Symbols
This manual contains up to three levels of safety instructions that must be observed in order to
avoid personal injury and/or damage to equipment or other property. These are:
DANGER Indicates a hazard that could result in death or serious bodily harm if the safety
instruction is not observed.
WARNING Indicates a hazard that could result in bodily harm if the safety instruction is not
observed.
CAUTION Indicates a hazard that could result in property damage if the safety instruction is
not observed.
In addition, the following symbols may appear on the product:
DANGER – Hazardous Voltage
ATTENTION – Consult the manual in all cases where this symbol is marked in
order to determine the nature of the potential hazards and any actions that
must be taken to avoid them
Protective earth (ground) terminal
Please read all safety instructions carefully and make sure you understand them fully before
attempting to use this product.
Cleaning Instructions
To clean the instrument exterior:
!Disconnect the instrument from the power source.
!Remove loose dust on the outside of the instrument with a lint-free cloth.
!Remove remaining dirt with a lint-free cloth dampened in a general-purpose detergent and
water solution. Do not use abrasive cleaners.
!Allow the instrument to dry completely before reconnecting it to the power source.
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vi

1. INTRODUCTION
With the introduction of the ORTEC®Alpha Suite®of integrated alpha spectrometers, we are
able to address the needs of any counting laboratory, large or small, upgrading or just starting
out. The ORTEC Alpha Suite consists of the Alpha Aria®, a single-channel NIM; the Alpha
Duo®, a compact, dual-channel benchtop system; the Alpha Mega®single-channel benchtop
module; and the Alpha Ensemble®, which can house one to four Alpha Duos and Alpha Megas
in any combination. The Alpha Ensemble can be mounted in a 19-inch rack or in the tabletop
enclosure in which it is supplied.
The latest advanced digital signal processing, together with a modular mechanical approach,
aligns value and performance with unparalleled configuration flexibility.
!Easy System Expansion — Any of these spectrometers can be added to existing ORTEC
systems simply by installing the latest CONNECTIONS Driver Update Kit (P/N 797230)
supplied with the instrument. Empty slots in the Alpha Ensemble chassis are covered by
easily removed blank panels. Expansion couldn’t be easier — simply slide an enclosure-
less version of the Alpha Duo or Alpha Mega into an available bay in the chassis, make
three simple connections, and the new module is ready for use.
!Performance
—Duo Each of the two Alpha Duo channels has a vacuum gauge; variable
detector bias supply (positive or negative); preamplifier; test pulser
generator with variable amplitude; and leakage current monitor. Each of
the two spectrometers has its own digital offset and conversion gain
settings for maximum flexibility. Each detector operates independently
with completely adjustable energy ranges from 0 to 10 MeV. Each pulse
generator is adjustable over a range representing 0 to 10 MeV. The bias
supply is adjustable from 0 V to ±100 V. The hardware controls, data
acquisition settings, detector bias, and leakage current are displayed and
controlled with ORTEC CONNECTIONS applications such as the accom-
panying MAESTRO®MCA Emulator or our AlphaVision®Alpha Particle
Spectrum Acquisition and Analysis for Microsoft Windows 7 and
XP SP3.
—Mega Except for its larger chamber and sample tray size, the Alpha Mega has
the same performance specifications as an individual Duo channel.
!High-Speed USB or Ethernet Connectivity — All three units connect to your PC via a
single, high-speed USB cable. (The Alpha Ensemble configuration contains an internal
USB hub.) Alternatively, you can use our USB-CONC CONNECTIONS Distance Extender
(purchased separately) to make a wired or wireless Ethernet connection without the dis-
tance limitation of USB communication.
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ORTEC®Alpha Duo®, Alpha Mega®, Alpha Ensemble®— Hardware User’s Manual 932505F / 0520
!Vacuum Connections and Monitoring — The Alpha Mega chamber has a single
vacuum connection and pressure gauge. The Alpha Duo’s twin chambers share a vacuum
connection, so both chambers operate at the same pressure; thus, any pumping, holding,
and venting operation affects both chambers. In the Duo, pressure in both chambers is
monitored by a single pressure-gauge head. The Alpha Ensemble chassis has an integral
vacuum manifold with a single external connector for attachment to a vacuum pump, and
four internal connectors for attachment to four Duos and/or Megas. This simplifies the
installation of the vacuum system, and reduces the possibility of vacuum leaks. The pres-
sure in each Duo in the Ensemble is controlled and monitored independently.
The vent/hold/pump functions for the Duo and Mega chambers are software controlled.
There are two operation modes: (1) selecting the vent, hold, and pump commands as
needed from a dialog; or (2) setting a target chamber pressure, then enabling an automatic
pressure control routine. At pressures >1 Torr to <13 Torr, a change of ±10% between the
target and actual pressure triggers the automatic correction. Outside this range, the
vacuum may not be controlled within 10%.
!Recoil Contamination Protection Option (Duo only) — Our Recoil Contamination
Avoidance Process (RCAP) is available as an option for the Alpha Duo. It employs a
reverse-biased sample tray (powered by a lithium coin battery on the tray underside; avail-
able separately from ORTEC) and careful control of the chamber pressure.
!Easy Maintenance and Decontamination — In the event of a contamination problem,
the affected Duo or Mega module can be removed for decontamination while you con-
tinue using the rest of the Alpha Ensemble chambers.
!Software Controlled Operation — All hardware and data acquisition settings are com-
puter controlled with MAESTRO, AlphaVision, or other ORTEC CONNECTIONS applica-
tions. The MCB Properties pages in MAESTRO display all pressure, bias, stabilizer,
digital offset, ADC, and pulser controls for the selected spectrometer. AlphaVision has a
specialized hardware panel that shows these readouts on one screen. (See also
Section 3.5.7.)
NOTE The Duo, Mega, and Ensemble do not have a vacuum interlock because bias
voltages are <100 V; we have not observed plasma discharges at these low
voltages.
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932505F / 0520 1. INTRODUCTION
1.1. About this Manual
This manual tells you how to set up and install the Alpha Duo and Alpha Ensemble, with empha-
sis on the Duo and Mega because they are the building blocks of the Ensemble.1
See the MAESTRO or AlphaVision User’s Manual for instructions on installing the software.
We assume you are familiar with alpha spectroscopy and sample preparation techniques. A good
starting reference and further reference materials can be found in “Measurement of Radio-
nuclides in Food and the Environment, A Guidebook,” Technical Reports, Series No. 295, ISBN
92-0-125189-0, Vienna IAEA.
!Chapter 2 of this manual provides instructions on installing and configuring the Alpha
Duo, Alpha Mega, or Alpha Ensemble and its operating software, connecting the detec-
tors to it, and connecting it to a vacuum pump.
!Chapter 3 tells how to control the sample chamber pressure, change samples, and operate
the Duo and Mega with MAESTRO.
!Chapter 4 discusses maintenance of both the Duo, Mega, and Ensemble, including how
to add a new Duo or Mega module to an Ensemble. This chapter also covers detector and
chamber decontamination, chamber replacement, and troubleshooting.
!Chapter 5 contains the system specifications and feature mask bits.
!Appendix A lists the Alpha chamber firmware commands for users who wish to write
custom software to control the unit with the ORTEC CONNECTIONS Programmer’s Toolkit
(A11).
!Appendix B tells how to switch to a detector of the opposite polarity.
1Hereinafter, the term Alpha chamber refers to individual Alpha Duo or Alpha Mega chambers; Alpha module
refers to either a Duo or Mega; and Alpha unit refers to either the Duo, Mega, or Ensemble.
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4

2. INSTALLATION
Setting up your Alpha Duo, Alpha Mega, or Alpha Ensemble is straightforward:
!Install the included CONNECTIONS Driver Update Kit.
!Install the accompanying version of the MAESTRO®MCA Emulation Software.
!Install AlphaVision or other ORTEC CONNECTIONS software, where applicable.
!Connect the Alpha Suite hardware to the host PC.
!Install the detector.
!Connect to the vacuum pump.
Install the CONNECTIONS Driver Update Kit before connecting the Alpha unit(s) to your PC.
If you have older versions of CONNECTIONS, MAESTRO, and/or AlphaVision on your PC,
remove them using the Control Panel’s software install/uninstall utility.
2.1. Install CONNECTIONS
The first step is to install the accompanying CONNECTIONS Driver Update Kit (P/N 797230)
according to its instruction sheet (P/N 932721). On the install wizard’s Instrument Setup page,
be sure to select the USB-based instruments family, otherwise the Alpha unit(s) will not com-
municate properly with your ORTEC software.
Be sure to read the entire instruction sheet. It discusses MCB support in detail; and explains
how to enable and disable the drivers for your ORTEC MCB(s) and share ORTEC MCBs across
a network. It also points you to information on selecting the proper network protocol for older,
TCP/IP Ethernet units. At the end of installation, you will be directed to restart the PC.
2.2. Install MAESTRO and Other Applications
Install MAESTRO, AlphaVision, etc., according to their respective user manuals.
2.3. Connect to the PC and Input Power
1) The Alpha unit’s ac power should be off and the cable disconnected from the mains outlet.
2) With the PC on, attach the USB cable between the Alpha hardware’s rear-panel USB connec-
tor and a high-speed (2.0) or full-speed (1.1) USB port on the PC rear panel. There is a
NOTE You must have Windows Administrator-level access to install ORTEC software.
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ORTEC®Alpha Duo®, Alpha Mega®, Alpha Ensemble®— Hardware User’s Manual 932505F / 0520
known issue with super-speed (3.0) USB connectivity and with connections to some PC
front-panel USB ports.
3) Connect the Alpha unit to ac mains power and turn its rear-panel On/Off switch on.
4) A series of “found new hardware” messages will be displayed. If Windows does not locate
the driver, a wizard will open. Choose the option that does not search the internet for the
appropriate driver, go to the next screen and select the “automatically find driver” option,
then follow the remaining wizard prompts to complete installation.
5) On the PC, run the MCB Configuration program from the Windows Start menu by selecting
MAESTRO, then MCB Configuration. MCB Configuration will automatically detect the
new Alpha chambers and add them to the list of detectors available to this PC. (If the new
chambers do not show up on the available detectors list, see the troubleshooting guide in
Section 4.3.)
6) When MAESTRO or AlphaVision is correctly communicating with the new Alpha module,
you should be able to select each of its spectrometers from the detector pick list within the
software application (at this point, there will be no spectrum to view). See Chapter 3 for
instructions on using the Alpha chambers and controlling data acquisition with MAESTRO
and AlphaVision.
2.3.1. Multiple-Duo / -Mega / -Ensemble Systems
Adding more Alpha modules to your system is fast and straightforward. Simply connect each
new module to a USB port on the host PC or to a powered USB hub.
Adding a new expansion module to an Alpha Ensemble takes about 3 minutes. Just power off the
Ensemble; remove a front-panel blank; extend the vacuum tube, USB cable, and power cable for
that bay and connect them to the expansion module; slide the new unit into the bay; and tighten
its front-panel screws. (For more detailed information, see Chapter 4.)
Remember that you must re-run the MCB Configuration program each time you add new MCAs
to your system in order to establish communication with them. See the MAESTRO or Alpha-
Vision User’s Manual for instructions.
2.4. Install the Detector
The ULTRA-AS series detectors normally used in Alpha chambers have a thin (500 D) contact
which is ion-implanted into the silicon surface. The contact is thus more rugged than that formed
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932505F / 0520 2. INSTALLATION
by an evaporated gold layer. If the silicon surface is scratched, however, the detector will be
damaged. Therefore, take reasonable precautions when handling these detectors.
If other types of detectors are used, read the detector’s instruction sheet before installing and
using it. If changing from a positive-polarity detector to a negative-polarity detector (or vice
versa), see Appendix B.
1) Turn the detector bias off for the chamber into which the detector is being installed.
2) Use clean plastic gloves and make sure the white protective cap for the detector is in place.
Align the center pin in the top of the chamber with the center socket in the detector connector
(threads are right-handed). Install the detector into the connector at the top of the chamber.
3) Remove the plastic cover, being careful not to touch the detector face (which will contami-
nate it).
2.5. Connect to the Vacuum Pump
The vacuum connector for the Alpha Duo and Alpha Mega is a 0.25 in. Swagelok®fitting. The
Alpha Ensemble has an NW-25 ISO-KF connector.
A rotary pump with an oil mist trap should be used. A pump displacement of 6.7 CFM
(190 liters/min) is required. The ALPHA-PPS-115 (or -230) and ALPHA-MINI-PPS are both
well-suited to this application.
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8

3. OPERATION
As a “quick start” for users already familiar with ORTEC spectroscopy applications, the first two
sections of this chapter tell how to use those applications to operate the Alpha Duo and Alpha
Mega vacuum chambers. A more detailed discussion of MAESTRO’s hardware and data
acquisition controls can be found in Section 3.5.
3.1. Controlling Chamber Pressure
The Duo and Mega have three pressure-regulation commands: Pump, Hold, and Vent. The
Pump setting connects the Mega chamber or both Duo chambers to the manifold; the Hold posi-
tion isolates the chamber(s); and the Vent position connects the chamber(s) to the atmosphere,
after which the doors can be opened.2
3.1.1. Manual
!MAESTRO — Go to the Alpha tab under Acquire/MCB Properties... and select the
vent, pump, and hold settings as needed from the Vacuum state droplist, using the
Actual vacuum readout to monitor chamber pressure. (See Fig. 9, page 16.)
!AlphaVision — On the Detector Grid, click on the desired alpha chamber, then click on
the Hardware icon on the outlook sidebar. Select the vent, pump, and hold settings as
needed from the Pump droplist. (See Fig. 10, page 17.)
3.1.2. Automatic
!MAESTRO — Go to the Alpha tab under Acquire/MCB Properties..., set a Target
vacuum between 1 Torr and 13 Torr, then click to mark the Vacuum monitoring
checkbox. If you set a target value outside this range, the chamber vacuum may deviate by
more than 10%.
!AlphaVision — On the Detector Grid, click on the desired alpha chamber, then click on
the Hardware icon on the outlook sidebar. Enter a Target vacuum between 1 Torr and
NOTE You may wish to write a .JOB file that automates the operations described below, par-
ticularly if you are controlling several Alpha Ensembles. See the chapter on .JOB files
in the MAESTRO User’s Manual.
2AlphaVision also has a detector group control interface that allows you to select one or more alpha chambers and
simultaneously change their pump status, turn detector bias voltage on/off, etc. See the AlphaVision user manual.
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ORTEC®Alpha Duo®, Alpha Mega®, Alpha Ensemble®— Hardware User’s Manual 932505F / 0520
13 Torr, then click to mark the Vacuum monitoring checkbox. If you set a target value
outside this range, the chamber vacuum may deviate by more than 10%.
The software will immediately begin using the vent, pump, and hold controls to maintain your
target vacuum ±10%.
3.2. Venting the Alpha Chamber(s)
3.2.1. Manual
!MAESTRO — Turn off the detector bias/pulser. Go to the Alpha tab of the MCB Pro-
perties dialog, click on the Vacuum state droplist, and select VENT. Use the Actual
vacuum readout to monitor chamber pressure.
!AlphaVision — Turn off the detector bias/pulser. On the Detector Grid, click on the
desired alpha chamber, then click on the Hardware icon on the outlook sidebar. On the
Pump droplist, select VENT.
3.2.2. Automatic
!MAESTRO — Turn off the detector bias/pulser. On the Alpha tab, unmark the Vacuum
monitoring, checkbox, then click on the Vacuum state droplist and select VENT.
!AlphaVision — Turn off the detector bias/pulser. On the Detector Grid, click on the
desired alpha chamber, then click on the Hardware icon on the outlook sidebar. On the
Pump droplist, select VENT.
3.3. Inserting a Sample into the Vacuum Chamber
1) Once the desired vacuum chamber(s) has been vented, open the door. Figures 1 and 2 respec-
tively show open Duo and Mega chamber with a detector, sample holder, and the series of
slots that allow you to adjust the sample-to-detector distance in 4 mm increments.
2) Slide the sample holder into the slot at the desired height. For optimum resolution, the sam-
ple-to-detector spacing should be at least equal to the detector diameter. The maximum spa-
cing is 44 mm. The sample trays shipped with the Alpha Duo are for 0.75 in. (19 mm) and
1 in. (25 mm) samples. The trays for the Alpha Mega can accommodate samples up to 4.2 in.
(106 mm), which can optionally be secured to the tray with the included removable clips.
3) Close the door, and use MAESTRO or AlphaVision to begin pumping. After a minute or two,
when the vacuum has reached a satisfactory value, you are ready to start data collection.
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932505F / 0520 3. OPERATION
3.4. Resolution Measurement and Calibration
The measurement of alpha-particle resolution should be performed in a vacuum with a uniform,
ultra-thin source located at a source-to-detector distance at least equal to the detector diameter.
Using old or inferior sources may cause apparently poor resolution and can lead to detector con-
tamination due to recoil sputtering. When using a source in an Alpha chamber, either for resolu-
tion measurement or system calibration, the following steps should be used for best results.
1) Place the source on a sample tray and insert it into the Alpha chamber. Placing the source as
far as possible from the detector helps reduce any solid-angle-related and/or count-rate
problems.
2) Evacuate the chamber.
3) Set the target bias and turn the bias on with the controls on the High Voltage property page in
MAESTRO (see Section 3.5.5) or the Hardware panel in AlphaVision. Wait 2 minutes.
4) Accumulate a peak containing at least 1,000 counts in the peak channel.
Fig. 1. Alpha Duo Sample Chamber Fig. 2. Alpha Mega Sample Chamber
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ORTEC®Alpha Duo®, Alpha Mega®, Alpha Ensemble®— Hardware User’s Manual 932505F / 0520
Fig. 3. Amplifier Tab
5) Determining the resolution requires measurement of the full-width at half maximum
(FWHM) of the peak. Use the Peak Info command in MAESTRO or the Peak Search and
Peak Fit features in AlphaVision.
3.5. MCB Properties in MAESTRO
This section discusses the hardware setup dialog you will see within MAESTRO, the Alpha-
Vision advanced chamber properties feature, and all other ORTEC CONNECTIONS software when
you click on Acquire/MCB Properties.... The MCB Properties dialog contains all of the com-
puter-selectable hardware controls including ADC setup parameters, high voltage on/off, cham-
ber pressure controls and readouts, and acquisition presets. Just move from tab to tab and set
your hardware parameters, then click on Close — it’s that easy. Note that as you enter characters
in the data-entry fields, the characters will be underlined until you move to another field or until
5 seconds have lapsed since a character was last entered. During the time the entry is underlined,
no other program or PC on the network can modify this value.
3.5.1. Amplifier
Figure 3 shows the Amplifier tab.
Set the amplifier Fine gain by
adjusting the horizontal slider or
entering the value, in the range of
0.25 to 1.00. The effective gain
is shown at the top of the Gain
section.
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932505F / 0520 3. OPERATION
Fig. 4. Amplifier 2 Tab
Fig. 5. ADC Tab
3.5.2. Amplifier 2
Figure 4 shows the Amplifier 2
tab, which accesses the advanced
shaping controls including the
InSight™ Virtual Oscilloscope
mode. This is typically not used
in alpha spectroscopy. For more
information on the InSight mode,
see the MAESTRO User’s
Manual.
3.5.3. ADC
This tab (Fig. 5) contains the
Conversion Gain, and Lower
and Upper Level Discriminator
controls. In addition, the current
real time, live time, and input
count rate are monitored at the
bottom of the dialog.
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ORTEC®Alpha Duo®, Alpha Mega®, Alpha Ensemble®— Hardware User’s Manual 932505F / 0520
Fig. 6. Stabilizer Tab
3.5.4. Stabilizer
The Stabilizer tab (Fig. 6) shows
the current settings for the gain
stabilizer (gain stabilization is
discussed in the MAESTRO
User’s Manual).
The value in the Adjustment
section shows how much adjust-
ment is currently applied. The
Initialize button sets the adjust-
ment to 0. If the value approaches
90% or above, the amplifier gain
should be adjusted so the stabili-
zer can continue to function —
when the adjustment value reaches
100%, the stabilizer cannot make
further corrections in that direction. The Center Channel and Width fields show the peak cur-
rently used for stabilization.
To enable the stabilizer, enter the Center Channel and Width values manually or click on the
Suggest Region button. Suggest Region reads the position of the marker and inserts values into
the fields. If the marker is in an ROI, the limits of the ROI are used. If the marker is not in an
ROI, the center channel is the marker channel and the width is 3 times the FWHM at this energy.
Now click on the appropriate Enabled checkbox to turn the stabilizer on. Until changed in this
dialog, the stabilizer will stay enabled even if the power is turned off. When the stabilizer
is enabled, the Center Channel and Width cannot be changed.
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