CsI-Advantage - Performance of High Resolution CsI(Na) Detectors

Energy resolution vs. Energy

Fig. 1 (above) shows how the energy resolution of CsI(Na) varies with energy. We measured the performance of the same crystal using regular and CsI-Advantage signal processing.

Non-proportionality

CsI-Advantage, just like regular CsI(Na), is a non-proportional scintillator. Fig. 2 shows the non-proportionality measured on the same crystal under regular and CsI-Advantage signal processing. Most noticeably, the non-proportionality is reduced for low energies, which is one of the contributing factors to the enhanced energy resolution of CsI-Advantage

Sample spectra - 3-inch detector

The spectra below were acquired on a 3-inch Ø, 3-inch tall CsI(Na)-Advantage crystal.

For energies of 662  and greater we also report the peak / Compton ratio. This is ratio of counts in the full-energy peak at its center value to the number of counts in the Compton scatter plateau just below the Compton shoulder associated with the gamma-ray energy.

It should be noted that this quantity does dependent slightly on the relative placement of the gamma-ray source and the detector. In the spectra shown below, the source was placed about 2-inch away from the front-face center of the 3-inch CsI(Na) detector. Source strengths were close to 1μCi.

⁵⁷Co

At 122 keV the energy resolution of this 3-inch crystal is 8.6% fwhm. The weak secondary γ-ray line at 136  is visible as a clearly distinct plateau and shoulder.

¹⁵²Eu

Zoom-in on the low-energy part of the ¹⁵²Eu-spectrum. At 122 keV the energy resolution of this 3-inch crystal is 8.6% fwhm.

¹³⁷Cs

No other scintillator, except for the very expensive La-halides, can provide an energy resolution of 5.5% fwhm and a peak-to-Compton ration of 14.1.

⁶⁰Co

⁶⁰Co spectrum and zoom-in on the double peak to show the excellent peak separation.

^natTh

Zoom-in on the 2615 keV line of ²⁰⁸Tl, a member of the thorium decay chain. Note the excellent peak definition for the 2615 keV line itself and for the associated escape peak, 511 keV below.

Short performance specifications

Applications

• Low-rate sample counting
• Low-background counting
• Radiation monitoring
• Count rates < 5,000 cps

Energy resolution

Cited below are typical and guaranteed values for CsI-Advantage detectors with 3-inch tall, 3-inch diameter crystals.

Energy	dE/E, typ. fwhm	dE/E, guar. fwhm
122 keV	8.6%	≤9.4%
662 keV	5.6%	≤6.0%
1333 keV	4.1%	≤4.5%
2615 keV	3.1%	≤3.4%

Energy resolutions are measured at count-rates ≤2000 cps. Full-energy peak pulse heights are adjusted to 750 mV at the ADC input (i.e. 75% of full scale range).

Specifications are subject to change. Contact factory before ordering.

Ordering information

CsI-Advantage complete detector system