Model 935 SAM

What is the correct calibration technique for the Model 935 MCA in Manual Mode?
The correct procedure to calibrate the SAM is to let the auto calibrate feature raise the voltage until the PMT gain is in the linear region with proper course/fine gain to perform the required response with Cs137. According to the detector manufacturer‘s recommendation this should be between 600 - 900 volts (including the 4x4x16 inch Sodium Iodide detector). The SAM will automatically do this - manual adjustments are unnecessary.
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What is the difference between a "Fine Energy Calibration" and a "Course Energy Calibration"?
The Fine Energy Calibration is done to allow the controller to understand the linearity of the NaI detector (due to our non-linear compression). Fine Energy Calibration need only be done once with a new detector. The Coarse Calibration is recommended prior to each use, although if conditions are similar, performance without recalibration will meet most requirements. To ensure optimal results during a Coarse Calibration, allow your Model 935 to run for 5 minutes before calibration.
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What are the measuring units respectively for dose and doserate of gamma & neutron?
The SAM allows user selection of units of dose: R (for REM) and Sv (for Sieverts). The system autoscales from pico, nano, micro, milli as required. The neutron measurements are in gross counts per minute.
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Is He-3 neutron detector available as an internal option and as an external option?
The He-3 neutron detector is available as an internal option for the Model 935 only. An external neutron detector is not available.
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What is the size, configuration and weight for Model 935 and detectors, both internal and external?
The heaviest Model 935 would contain two internal detectors, one He-3 neutron detector and one internal 1.5"x 2.0" NaI detector. This configuration weighs approximately 5½ lbs. The Model 935 with external detectors weighs approximately 4 lbs.
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What is the energy measuring range for He-3 neutron detector in the Model 935?
The SAM measures neutrons of all energies. It is more sensitive for slow neutrons such as those associated with Sensitive Nuclear Materials (SNMs). The detector sensitivity specification is 12.7cps/nV, the units of n are neutrons/cc, V is velocity in cm/sec. Multiplying this out yields neutrons/cm squared.
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How many channels of data memory are offered in Model 935?
The Model 935 offers 256K x 16 bits, battery backed up. This is enough spectra storage for approximately 300 alarm events (spectra, complete mca report, doserate report).
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How many channels of ADC are offered in Model 935?
The Model 935 uses a 14-bit ADC, 16 K channels.
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What is the difference between Quantum MCA and Quantum Gold Software Packages?
Quantum MCA is a very complete MCA package for Windows based PCs. It will control the SAM systems (Model 905 and Model 935) from the PC, collect data into the PC and provide Qualitative Analysis capability. The Quantum Gold option adds Quantitative Analysis capability with efficiency correction for detector and counting geometries.
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What is the minimum detectable level for the Model 935?
The Model 935 can detect down to 1nR/hr. However, most backgrounds are going to be in the range of 1-10 uR/hr. The published specification for the Model 935 is .5uR/hr - 10mR/hr.
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What calibration sources will I need for my Model 935?
If you plan to use the same detector, you will not need calibration sources. However, for fine calibration or areas with significant temperature changes, BNC recommends a calibrated Cs137 and an Eu152. The Cs137 is used for the coarse calibration and dose rate calibration and the Eu152 is used for the fine calibration. BNC offers a source kit, Part Number 6918, with a 10uC calibrated Cs137 source and a 1uC Eu152 source.
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Can the Model 935 give dose rate on a per isotope basis?
Yes. It shows total dose, total dose rate and all isotope specific information as well.
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How many cables are there with the Model 935? What are the connectors and functions?
With the external detector options on the Model 935, the external detectors use a single multiconductor cable with a LEMO connector at each end of the cable. The LEMO connectors feature quick disconnect, rugged and reliable operation. The detectors use the standard Lemo connector on the base of the detector. With an internal detector option, there are no cables.
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What is the standard cable length for external detectors?
Our standard cable lengths are 8 feet, 30 feet and 50 feet.
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Can I use the Model 935 to look at total counts within a particular region of interest?
The Model 935 can operate in several modes. If you are in the real-time mode (monitor, detail, or surveillance), reviewing the current spectra or any previously collected spectrum, press F4 (MCA) and the spectra will be pulled into the MCA Display. Then perform a peak analysis and nuclide ID of the spectra, set ROI around each peak, report the peak energy, and report the net cpm for each peak
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Does the Model 935 ship with wall chargers suited for the US, or all countries?
BNC offers power/battery chargers for Europe, Asia and the United States. Contact the factory for other needs.
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Can the Model 935 count gamma and neutron at the same time?
Yes. The Model 935 supports a neutron detector and gamma detector simultaneuosly. The He-3 neutron detector is charged to 20 atmospheres.
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Can the Model 935 operate in high background environments?
The SAM performs very well in moderately high backgrounds as it subtracts the natural background and strips off the compton in real time. It will report isotope intensity relative to background and also report individual radionuclide contributions to a total dose.
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How many detectors can I attached to the Model 935 simultaneously?
The Model 905 and 935 operate with one detector. However, for applications that require multiple detectors in multiple locations, a network of systems throughout a facility can be monitored by a control unit. Contact the factory for networked area monitor applications.
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Can I use a 935 controller with any detector and still obtain realtime collection and analysis?
No. The Model 935 is designed for use with a particular type of NaI detector that incorporates a highly efficient, proprietary high voltage bias supply built into the base of the detector. The Model 935 control unit provides 12 V dc power to the detector base along with a 0 - 1 Volt reference that controls the bias voltage for detector operation. The signal does, however, come back from the detector to the controller preamplifier/amplifier much like other systems. This system allows for fully automatic calibration where the Model 935 resets the bias voltage and amplifier gain settings.
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Can a Model 935 easily and quickly detect Thorium, Radium and Uranium?
Yes, are all easily detected and analyzed. First selected the correct isotopes from the library and placed it in the lookup list. There are several isotopes of each of these elements in the Model 935 library.
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Can you discriminate between the lines used in identification of radioisotopes?
Yes, you can enable the lines that you want to use for identification. However, if the library has a low energy line and a higher energy line both enabled for a given isotope, you may not be able to identify the isotope if the source is in a container that shields the low energy line.
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Why would I change the lines used to identify an isotope?
The Model 935 gives you control over your application. This is what makes the SAM technology very powerful. The user can change lines or add lines without returning the instrument back to the factory. Impurities and daughters in the Actinide, Thorium, and Uranium series can create uncertainty. Typically we use 2 or more lines to identify an isotope. Identification with the Model 935 is more sensitive and subject to fewer false counts than other instrumentation because of compression and hysteresis.
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Can I detect Am241 in the presence of Cs137?
Yes. The Model 935 allows modification of the isotopic radiation lines in its library. One can very easily enable or disable a particular energy line in order to optimize results. This is helpful when two or more lines are very close. In this case, however, you would not need to modify the lines. Good results can be obtained without altering the standard library since there is ample seperation between all major lines (Cs-137: 662 and 32 keV; Am-241: 59.5 and 26 keV). Request a “Test Summary Sheet - Am241 for supporting data.
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I am connecting my SAM to a PC. What is a Null Modem Cable?
A null modem cable is what is sometimes called a cross cable. It has pins 2 & 3 crossed from one end to the other so that it can connect one PC to another PC. The cable and com port can be tested by connecting two PC”s and verifying communications using Windows HyperTerminal program on each PC.
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What if I connect my SAM to a PC, and there is no activity on the SAM display?
If there is no activity on the 935 screen, then as far as the 935 goes there has not been an attempt to communicate with it. See Remote-Com.jpg for an example of what the screen might look like after the hardware search program has completed its update. The user must click on the UPDATE command button in the Hardware search program. See the attached file Remote-NoCom.jpg for what the blank screen looks like if the 935 does NOT receive any communications.
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What are the pin-outs for the SAM Battery and Charger?
The 4 pin battery connector has the following pin-outs: (1) +Volts-red (2) Thermister-Yellow (3) Blank (4) Ground, The 3 pin charger connector has the following pin-outs: (1) +Volts-Orange (2)Ground-Black (3)Thermister-Yellow
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Why wont Autoload or Hardware Search work with my Windows 2000 PC?
Microsoft has set up 2000 so that program "controls" will not work unless an entry is made in the Windows Registry saying the they were properly installed. Also, some of the support programming is in DLL files (which required for the program to be able to talk to the hardware). Therefor, unlike Windows 98, neither Autoload or Hardware Search will run without a full Quantum MCA, Quantum NaI or Quantum Demo install.
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WIs the SAM compatible with Windows 2000?
Yes, installing the Quantum Demo will allow all the necessary programs in your Windows 2000 machine to work. Contact BNC for a copy.
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How do I clear all my stored alarms?
By going into the Utility Menu, you have an option to “Clear All Spectra”. This will clear all the respective alarms at the same time.
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Does the SAM 935 detectors have any “aperture” setting or field-of-view? For example, if I just point the external NaI detector or internal detector at something, or down towards the ground, how much area at a given distance am I covering?
The field of view in an image sense is limited by aperture. However, the aperture of the NaI detectors is essentially 4 pi with some sensitivity lost due to the attachment of the photo multiplier tube (PMT). Since we want the most sensitivity achieve able, we generally point the detector 180 degrees from the PMT - dead ahead. The next thing to consider is the inverse square law. Therefore, if you are pointed toward a flat plane (wall of a room, segment of earth below) intensity of the signal is going to fall off inversely to the distance squared. If you are looking at a long wall with a given source, and standing in the center, then the end of the wall will give less intensity because of increased distance - the detector if pointed dead ahead is just as sensitive looking out all sides in every plane (except minor shielding at the rear from the PMT). A camera has varied sensitivities to different colors of light regardless of the aperture. The NaI detector will have varied sensitivity due to different photon energies. X-ray energies below 100 keV will be somewhat attenuated from the heavy construction of the detector housing on the side (thin window on front) - giving the best response to x-rays dead ahead and about 60 degrees off the forward plane in every direction. This is a minor problem because for a given dose rate the number of photons are inversely proportional to the photon energy. Therefore, a larger effect will be seen with high-energy gamma radiation. This is often justification for a larger detector. Not only is the field of view larger but the number of photons interacting with the NaI crystal is increased. Sensitivities down to background levels of radiation are nearly flat as a function of energy when using a 4x4x16 inch detector (out to ~1 MeV). At this point you can see why sensitivity does NOT go to zero at any point on the case nor can you say the center is maximum - other than the minor fluxuations due to the energy issues explained above. The inverse square law is the most important consideration.
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What are the external measurements of the 1.5x2 inch detector, external detector?
2.5" diameter x 10" long.
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Is there a way to convert microR/hr of the SAM 935 to nGy/hr?
The SAM only reports either R/hr or Sv/hr. However, since Gy (gray) is related to Sv the same way Rad is related to Rem, then selecting Sv/hr will give you the equivalent of Gy/hr. They are equivalent only for Gamma where the "Q factor" is equal to 1. Sv = Gy x Q x N Where Q is equal to 1 for gamma, and N =1 (as per ICRP).
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Can the SAM 935 substitute HPGe in the laboratory in the presence of a shield and with QuantumGold?
Yes to some extent, that is if the user has simple spectra with well seperated energy lines with no overlap as seen on a NaI detector with 8% resolution.
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What is the power draw on the SAM 935?
Measured from the AC line at 115 volts. Power is equal to volts times amps.
0.23 amps normal running
0.36 amps charging the battery
0.11 amps with battery mostly charged
0.09 amps with charger not connected to anything

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What is the voltage and wattage provided to the unit by the DC adaptor?
14.0 VDC @ 670 mA
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What is the typical power draw of the unit in normal operation (from battery or adaptor)? This applies to the operation of the device, not the recharging of the battery, if that has been separated.
7.2 Watts
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How does the V11 firmware autocalibration work?
Auto calibration is performed by a very small activity DOT exempt radioactive source positioned near the NaI scintillator. This is usually Co60 although Cs137, K40 and Th232 can be used. A region of interest (ROI) is established to track changes in temperature that would result in up to +/- 10% shifts in energy calibration. The ROI is established such that the isotopic peak of the calibration source is in the center of this ROI. As an example Co60 uses 32 channels with the 1332 keV peak centered in the ROI. At the beginning of calibration a buffer receives counts in the ROI and when reaching 1000 counts makes a correction to the fine gain. This places the Co60 peak in the appropriate channel for calibration. As long as the SAM is operated in any one of the 3-search modes calibration will continue to take place in the background (as described above).
(Back) Does the imbedded stabilization source reduce the sensitivity in the new version 11 SAM 935?
Basically, the difference in sensitivity between earlier versions and version 11 SAM 935 is so insignificant that it cannot be measured. We have taken measurements in the vicinity of a calibration source (external) as well as the current stabilization source (imbedded) and can offer some generalizations as to how each situation may affect data acquisition using the version 11 SAM 935 while performing common tasks.

For short to long term (1-20 minute) acquisitions there is no discernible difference in sensitivity. The imbedded source is only 10-20 nCi of Cs137. This source is located several inches away from the 3x3 inch detector crystal and contributes about 350 nrem/h in the photopeak which is a small fraction of the total background and makes it difficult, if not impossible, to see any loss in sensitivity. Short runs of 1-2 minutes on another Cs137 source with intensities of about 50 nrem/h yield solid statistics (low uncertainties with firm identification). Lower intensities can be measured with longer acquisitions (a longer background must be taken as well).

When searching second by second you will see an occasional flash of Cs137 (averaging about 300-400 nrem/h). This was observed when lowering the 500 nrem/h threshold default and will not pose any problem for those using the threshold default (for high confidence you want to see Cs137 almost every second). For those wanting to push the limit of the 3x3 detector, lowering the threshold to 100 nrem/h would allow you to discern the difference between a Cs137 source and the embedded source. This is done by observing both the frequency and the dose rate of the external Cs137 source while searching.

An alternative approach for those needing the ultimate sensitivity without interference from the embedded source is to use K40 as the stabilization source. If your application allows, place KCl around the detector (about 250 grams is sufficient) to create an excellent high energy reference far removed from other background and sources of interest. The version 11 SAM935 can be purchased without an imbedded source for this application.

Can the SAM 935 identify Polonium 210?
Yes, Identification is best done with a large detector since Po210 has a very low abundant gamma energy line. However, you can also do it with the internal detector if you acquire for 5 minutes or more depending on the activity of the sample. You will need to first add the isotope to the library. Press F2 in Edit Isotope Library to add an isotope. (1) Name the isotope (Po210), (2) put in the half life (138 days), (3) enter the energy line (803 keV) and (4) enter the intensity (0.0012%). 100 nrem/hr should be enough material to give you a small dose rate.