Next Generation Alpha Particle Counter

 

Advanced Alpha Particle Emission Metrology

The UltraLo-1800 is a revolutionary new design for low background alpha particle counters that employs electronic background suppression to drive achievable background rates to 0.0001 alphas/cm2/hr and below. This is a factor of 50 or more better than can be achieved by the conventional proportional counter systems that are currently available, and results in:

  • Dramatically reduced counting times
  • Repeatable & reliable measurement results
  • Advanced sample analysis
  • Robust data management
 

Applications

Materials Screening

Monitor your ultra low alpha materials (0.001 alphas/cm2/hr) with accurate measurements in just one day.

Quality Control

Ensure that the materials you receive satisfy your design requirements by using the most sensitive instrument available.

Quality Assurance

Certify that the product you ship complies with your customers’ specifications.

 

THEORY // Electronic Background Suppression

The UltraLo-1800 employs the patented technique of electronic background suppression, which drives achievable background rates to 0.0001 alphas/cm2/hr and below. This is a factor of 50 or more better than can be achieved by the conventional proportional counter systems that are currently available.
Through the use of novel, dual channel pulse-shape-analysis techniques, the UltraLo- 1800 is able to distinguish between alpha particles emitted from the sample under test, and those emitted from other parts of the counter structure.
Keep reading to learn more about why backgrounds are important in alpha particle counting, and how the technique of electronic background suppression works in the UltraLo- 1800.
 

Alpha Counting Challenges

  • Materials used to construct alpha counters will emit alpha particles, contributing to the background signal of the instrument.
  • The general approach is to make two measurements, with and without the sample, and subtract them to remove the background.
  • But what happens when sample activity levels are much lower than background levels?
    • Published proportional counter backgrounds are 3-5 alphas per hour.
    • Yet wafer level materials are currently screened at 6 alphas per day.
  • Detecting such a small signal hidden in such a large background requires very long counting times and is prone to error from statistical fluctuations.
Imagine if you could eliminate the background by only counting alpha particles coming from the sample, and not those coming from the counter!
 

Current proportional counter technology

  • Sample sits under thin window.
  • Array of fine anode wires biased at HV creates a high field region and provides a gain mechanism (through electron multiplication) for better signal-to-noise.
  • But this means that all alpha emissions look the same, because the pulse shape is dominated by the gain mechanism!
 

UltraLo-1800 takes a novel approach

Fundamental difference: UltraLo-1800 operates in ionization mode, not proportional mode.
Sample sits within the active counting region – no entrance window.
Geometry of counter is designed to exaggerate differences in signals generated by alphas emitted from various parts of the counter.
Two signal channels to further distinguish between alpha emission locations.
 

UltraLo-1800 Technology

  • Emissions from different areas look different, because pulse shape isn't dominated by gain, but rather by drift distance.
  • Dual-channel pulse shape analysis reveals origin of alpha particles.
  • UltraLo-1800 actively rejects events not coming from the sample.
  • Further pulse analysis gives energy of the alpha particle.
 

Features

The UltraLo-1800 is a windowless, ultra low background alpha particle counter designed to measure the alpha particle emissivity of solid materials.

  • Electronic Background Suppression: Dramatically reduces counting times; measure ULA samples in hours or days, not weeks or months.
  • Advanced sample analysis: Energy information allows for the identification of isotopes on sample surfaces
  • Complete instrument control via CounterMeasure: Run management, data analysis, system health metrics, and much more.
 

CounterMeasure // Control Software

CounterMeasure – the interface to the UltraLo-1800 system – is a powerful data collection, analysis, and instrument control application. The software capabilities include the display of: energy spectra, time stamped events, system health metrics, measurement error evolution, and much more. Sophisticated yet intuitive, this tool provides users with unique insights into their alpha particle emission measurments.

  • Robust Data Management: Easily access and review both current and historical measurement data.
  • Data Export: Generate and save datasets in convenient ASCII format.
  • Report Generation: Save measurement results to PDF reports.
 
 
CounterMeasure in action (accelerated time lapse)
 

Measurement Data Display Capabilities: Emissivity & Alpha Counts

 
Sample Description:ULA coated metal sheet
Sample Area:707 cm2
Run Length:48 hrs
Final Emissivity:0.00068 (a/cm2/hr)
Final Error:0.00015 (a/cm2/hr)

Estimate of sample emissivity (with error bars) is continuously updated as the measurement proceeds.

Sample alpha counts time stamped throughout measurement.

 
 

Measurement Data Display Capabilities: Energy Spectra

  • Amplitude of signals is proportional to alpha particle energy deposited in gas.
  • The UltraLo measures the energy of every alpha particle and generates energy spectra for every sample measured.
  • Identify surface vs bulk contamination issues.
Th-230 Spectrum Rn-222 Spectrum
 
 

Specs

Performance Category

Required counting time for measurement of ULA (0.001) sample1
Required counting time for measurement of LA (0.01) sample1
Typical counter efficiency
Energy Resolution (230Th source)
Energy sensitivity range
Sample sizes (typical min – max)

Specification

(50%) 6hrs, (25%) 24hrs, (12.5%) 90hrs – (meas accuracy) time
(50%) 30 min, (25%) 2.5hrs, (12.5%) 9hrs – (meas accuracy) time
> 90% of 2pi
< 9% FWHM (at 4.6MeV)
1.5-10 MeV
300mm wafer (707 cm2) – 1800 cm2
 
1 - Sample assumed to be 300mm wafer (count times drop by factor of 2.5 when using max sample area)

Attribute

Minimum sample size (typical)
Maximum sample size
Maximum sample weight
Maximum sample thickness
Counting gas
Gas pressure
Line Voltage
Power consumption (Instrument)
Power consumption (Laptop)
System dimensions (L x W x H)
Weight

Requirement

300mm wafer (707cm2)
1800cm2
20 lbs (9 kg)
0.25 in (6.3 mm)
Argon (boiloff recommended)
21psi (150kPa) ± 5%
100-240 (VAC) 50/60Hz
50 W (100 W maximum)
30 W
65 in x 35 in x 27 in (165 cm x 89 cm x 69 cm)
360 lb (163 kg)
 
 

Counting system includes

Counting Module - Sample handline, measurement chamber, signal processing electronics.
Support Module - Power supplies, gas control, etc
Laptop - Windows 7 professional, x64
CounterMeasure - Sophisticated data collection, analysis, and instrument control application
Support - One year of service and support
 
 

Resources & Downloads

 

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