Minimization of thermal deformation in crystal optics for high repetition-rate FEL

Journal Article · Wed Jan 01 04:00:00 EST 2025 · Journal of Synchrotron Radiation

OSTI ID:3008274

Zhang, Lin ^[1]

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1. SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Linac Coherent Light Source (LCLS)

Minimizing thermal deformation in X-ray crystal optics is crucial for preserving coherence and wavefront in high-repetition-rate free-electron lasers (FELs). This study presents two approaches to reduce pulse-by-pulse transient thermal deformation in diamond crystals used in cavity-based X-ray FELs (CBXFELs): (1) cryogenic cooling with liquid nitrogen (LN₂), and (2) second-order correction via focusing optics. We revisit the temperature-dependent thermal-mechanical properties of diamond and silicon, implement a finite-element analysis (FEA) method to accelerate convergence to a quasisteady-state regime. Results show that LN₂-cooled diamond crystals meet the stringent deformation requirement of less than 15 pm RMS for the pulse at mJ scale at 1 MHz repetition frequency, and up to 1.5 mJ for 100 kHz. Second-order correction by using focusing elements within the cavity can reduce the impact of thermal deformation for both liquid nitrogen and water cooling.

• Research Organization: SLAC National Accelerator Laboratory (SLAC)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 3008274
• Journal Information: Journal of Synchrotron Radiation, Journal Name: Journal of Synchrotron Radiation
• Country of Publication: United States
• Language: English

Related Subjects

X-ray crystal optics
free electron laser
liquid nitrogen cooling
pulse-by-pulse transient thermal deformation
second-order correction