Sensitive Nonlinear Iterative Peak-clipping (SNIP)

Table of contents

  1. Introduction
  2. How to use
  3. Behavior
  4. Method
  5. References

Introduction

Sensitive Nonlinear Iterative Peak-clipping (SNIP) estimates a slowly varying spectral background by repeatedly clipping peak-like structures from a transformed spectrum.

How to use

  1. Upload data, then open Processing Page.
  2. Enable Baseline removal.
  3. In Select baseline removal function, choose SNIP.
  4. Set SNIP Iterations.
  5. Apply the processing workflow to subtract the estimated baseline.

Behavior

SNIP estimates a slowly varying background by iteratively clipping peaks from a transformed spectrum. Increasing SNIP Iterations allows the baseline estimate to remove wider peak structures, usually producing a smoother and lower background.

Method

SpectraGuru applies a log-log-square-root transform before iterative clipping:

\[v = \log(\log(\sqrt{\max(y,0)+1}+1)+1)\]

The clipping update replaces each point with the smaller of the current value and the average of points at a symmetric offset:

\[v_i \leftarrow \min\left(v_i,\frac{v_{i-k}+v_{i+k}}{2}\right)\]
Parameter Tunable or fixed Implementation
SNIP Iterations Tunable Default 50, UI range 10-200
Transform Fixed Log-log-square-root transform with inverse transform after clipping
Baseline action Fixed Estimated baseline is subtracted from each selected spectrum

References

  1. Morhac, M., Kliman, J., Matousek, V., Veselsky, M., & Turzo, I. (1997). Background elimination methods for multidimensional coincidence gamma-ray spectra. Nuclear Instruments and Methods in Physics Research Section A, 401(1), 113-132. https://doi.org/10.1016/S0168-9002(97)01023-1