---
title: "January 5, 2024 - SAM 940 plus: Response Curve for the Nal Detector"
date: 2024-01-04T21:43:32Z
modified: 2025-10-01T04:48:43Z
permalink: "https://www.berkeleynucleonics.com/january-5-2024-sam-940-plus-response-curve-nal-detector/"
type: post
status: publish
excerpt: ""
wpid: 13587
categories:
  - Uncategorized
featured_image: "https://www.berkeleynucleonics.com/wp-content/uploads/press_response_curve_010424.jpg"
---

One aspect that measures the efficiency of isotope identifiers or RIIDS is their response curve. The response curve below refers to how the detector exhibits a sensitivity to a radioactive source at 5 cm. Berkeley Nucleonics offers a variety of isotope identifiers with different detector sizes (2×2, 3×3 etc) and materials (CeBr3, CLYC:Ce, etc). However, the response graph described here is for a standard 940plus with a 2” x 2” Nal detector. There are two curves – One is theoretical and the other is experimental. There is about a 25% – 30% discrepancy due to the quantum efficiency of the PMT. The Y-axis unit is the “probability.” For instance, if one gamma photon is generated from the CRM source at a distance of 15 cm from the center of the detector surface, the y-axis value is the probability of the gamma photon.

**Gamma interaction probability as a function of energy**

Experimental probability of [SAM 940+](https://www.berkeleynucleonics.com/sam-940-plus) is about 25% to 30% of theoretical data (QE of PMT: 25-30%)

![](https://www.berkeleynucleonics.com/wp-content/uploads/press_response_curve_010424.jpg)

_**Looking for more information about the SAM 940 plus? Please contact our technical experts and review our datasheet, found on the product page linked below.**_

[_**SAM 940+ Product Page**_](https://www.berkeleynucleonics.com/sam-940-plus)