# Learner lab record: Reaction yield and detector-efficiency audit

Course: Introductory nuclear physics and reaction evidence

Name: ____________________  Date: ____________________  Group: ____________________

## Investigation question

How do beam rate, target thickness, cross section, and detection efficiency combine into an expected count rate?

## Setup

Use the reaction-yield laboratory. Begin in the thin-target regime, vary one factor at a time, and keep physical reaction yield separate from detector counts.

## Variables

| Variable | Role | Unit |
| --- | --- | --- |
| Beam particle rate | independent | particles/s |
| Target areal density | independent | nuclei/area |
| Reaction cross section | model input | area |
| Reaction and detected rates | dependent | events/s and counts/s |

## Predict before changing controls

1. Predict the yield response to doubling beam rate in the thin-target limit.

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2. Predict what detector efficiency changes and what it leaves unchanged.

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## Observation table

| beam rate | areal density | cross section | reaction rate | efficiency | count rate |
| --- | --- | --- | --- | --- | --- |
|   |   |   |   |   |   |
|   |   |   |   |   |   |
|   |   |   |   |   |   |
|   |   |   |   |   |   |
|   |   |   |   |   |   |
|   |   |   |   |   |   |

## Analyze

1. Which runs demonstrate linear scaling?

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2. When would the thin-target approximation fail?

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3. Why are counts not automatically proof of the proposed reaction channel?

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4. Name two background or calibration controls.

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## Evidence-bounded conclusion

Changing ___ by a factor of ___ changed modeled reaction rate by ___; detection efficiency changed ___ but not ___.

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