Design and performance of a double-solenoid magnetic bottle photoelectron spectrometer for attosecond metrology.

The article focuses on the design, optimization, and performance evaluation of an in-house developed double-solenoid magnetic bottle electron time-of-flight (MBe-TOF) spectrograph for attosecond pulse characterization. This spectrograph employs a strong Sm₂Co₁₇ permanent magnet combined with a soft iron cone and two solenoids—one inside vacuum and one outside—to create a smooth magnetic field profile that enhances collection efficiency (~25%) and energy resolution (better than ~60 meV at ~15 eV photoelectron energy) while enabling ultrahigh vacuum (~5 × 10⁻⁸ mbar) with a moderate-capacity turbo-molecular pump. The device was successfully used to characterize attosecond pulse trains generated from the 15th to 25th odd high-harmonic orders in argon gas via the "Reconstruction of Attosecond Beating by Interference of Two-Photon Transition" (RABBITT) technique, measuring pulse durations around 260 attoseconds (FWHM). The design offers a compact, efficient setup suitable for attosecond metrology and pump-probe studies with relaxed vacuum requirements compared to previous spectrographs.