Adaptable phase retrieval for coherent transition radiation spectroscopy based on differentiable physics information

Fuente: arXiv
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Main Authors: Aguilar, Ritz Ann, LaBerge, Maxwell, Doepp, Andreas, Debus, Alexander, Bi, Zewu, Bussmann, Michael, Irman, Arie, Schramm, Ulrich, Kelling, Jeffrey
Format: Preprint
Published: 2026
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author Aguilar, Ritz Ann
LaBerge, Maxwell
Doepp, Andreas
Debus, Alexander
Bi, Zewu
Bussmann, Michael
Irman, Arie
Schramm, Ulrich
Kelling, Jeffrey
author_facet Aguilar, Ritz Ann
LaBerge, Maxwell
Doepp, Andreas
Debus, Alexander
Bi, Zewu
Bussmann, Michael
Irman, Arie
Schramm, Ulrich
Kelling, Jeffrey
contents Coherent transition radiation (CTR) spectroscopy is a critical diagnostic for characterizing the longitudinal structure of relativistic electron bunches in laser-plasma and conventional accelerators. In practice, recovering the bunch profile from a measured CTR spectrum is an ill-posed phase-retrieval problem. Traditionally, this is addressed using Gerchberg-Saxton (GS)-type iterative algorithms. However, these implementations often rely on explicit inverse propagators, making them difficult to adapt to sophisticated experimental forward models. In this work, we introduce a flexible gradient-based framework for CTR phase retrieval. By leveraging a differentiable forward model, we propose a phase-only gradient descent (GD-Phase) approach that enforces the measured spectral amplitude as a hard constraint while optimizing the Fourier phase under physical real-space priors. Using synthetic CTR spectra spanning multi-peaked and strongly modulated profiles, we benchmark GD-Phase against traditional GS and a real-space amplitude-parametrized gradient descent (GD-Amp) algorithm. Unlike traditional methods, this formulation allows for the seamless inclusion of arbitrary differentiable experimental effects into the reconstruction loop. We demonstrate that this physics-informed approach not only reproduces the fidelity of GS methods but also establishes a robust baseline for incorporating multi-diagnostic constraints and uncertainty quantification. This enables the systematic extension to higher-dimensional, multimodal, and uncertainty-aware diagnostics, facilitating fast and scalable phase retrieval in realistic experimental settings.
format Preprint
id arxiv_https___arxiv_org_abs_2604_25489
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Adaptable phase retrieval for coherent transition radiation spectroscopy based on differentiable physics information
Aguilar, Ritz Ann
LaBerge, Maxwell
Doepp, Andreas
Debus, Alexander
Bi, Zewu
Bussmann, Michael
Irman, Arie
Schramm, Ulrich
Kelling, Jeffrey
Accelerator Physics
Machine Learning
Coherent transition radiation (CTR) spectroscopy is a critical diagnostic for characterizing the longitudinal structure of relativistic electron bunches in laser-plasma and conventional accelerators. In practice, recovering the bunch profile from a measured CTR spectrum is an ill-posed phase-retrieval problem. Traditionally, this is addressed using Gerchberg-Saxton (GS)-type iterative algorithms. However, these implementations often rely on explicit inverse propagators, making them difficult to adapt to sophisticated experimental forward models. In this work, we introduce a flexible gradient-based framework for CTR phase retrieval. By leveraging a differentiable forward model, we propose a phase-only gradient descent (GD-Phase) approach that enforces the measured spectral amplitude as a hard constraint while optimizing the Fourier phase under physical real-space priors. Using synthetic CTR spectra spanning multi-peaked and strongly modulated profiles, we benchmark GD-Phase against traditional GS and a real-space amplitude-parametrized gradient descent (GD-Amp) algorithm. Unlike traditional methods, this formulation allows for the seamless inclusion of arbitrary differentiable experimental effects into the reconstruction loop. We demonstrate that this physics-informed approach not only reproduces the fidelity of GS methods but also establishes a robust baseline for incorporating multi-diagnostic constraints and uncertainty quantification. This enables the systematic extension to higher-dimensional, multimodal, and uncertainty-aware diagnostics, facilitating fast and scalable phase retrieval in realistic experimental settings.
title Adaptable phase retrieval for coherent transition radiation spectroscopy based on differentiable physics information
topic Accelerator Physics
Machine Learning
url https://arxiv.org/abs/2604.25489