A highly sensitive electron spectrometer for crossed-beam collisional ionization: A retarding-type magnetic bottle analyzer and its application to collision-energy resolved Penning ionization electron spectroscopy

Yamakita, Yoshihiro; Tanaka, Haruko; Maruyama, Ryo; Yamakado, Hideo; Misaizu, Fuminori; Ohno, Koichi

doi:10.1063/1.1305819

Cited by 31 publications

(12 citation statements)

References 57 publications

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“…Penning electrons were collected by Ômagnetic bottle effectÕ utilizing an inhomogeneous magnetic field with a permanent magnet (80 mT) and a solenoid (1.4 mT) [18] for the better efficiency of electron counts. Electron counts as functions of the voltage for the retarding electron field and time-of-flight (TOF) from the chopper plate were accumulated with a multichannel scalar for two parameters [13].…”

Section: Experiments and Calculationmentioning

confidence: 99%

Collision-energy-resolved Penning ionization electron spectroscopy of OCS with He*(23S) metastable atoms

Kishimoto

Horio

Maeda

et al. 2003

Chemical Physics Letters

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Section: Experiments and Calculationmentioning

confidence: 99%

Collision-energy-resolved Penning ionization electron spectroscopy of OCS with He*(23S) metastable atoms

Kishimoto

Horio

Maeda

et al. 2003

Chemical Physics Letters

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“…This leads to a surface temperature rise of ∆T ≈ 5.7 K at the end of a laser pulse, which is negligible in terms of thermionic electron emission. All high energy background effects originating from the radioactive source, can be efficiently filtered when placing the 229 Th source in a magnetic bottle [39], as only electrons of below ∼100 eV kinetic energy will follow the magnetic field lines. The corresponding experimental detection scheme is shown in Fig.…”

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confidence: 99%

A Laser Excitation Scheme for Th229m

et al. 2017

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Direct laser excitation of the lowest known nuclear excited state in 229 Th has been a longstanding objective. It is generally assumed that reaching this goal would require a considerably reduced uncertainty of the isomer's excitation energy compared to the presently adopted value of (7.8 ± 0.5) eV. Here we present a direct laser excitation scheme for 229m Th, which circumvents this requirement. The proposed excitation scheme makes use of already existing laser technology and therefore paves the way for nuclear laser spectroscopy. In this concept, the recently experimentally observed internal-conversion decay channel of the isomeric state is used for probing the isomeric population. A signal-to-background ratio of better than 10 4 and a total measurement time of less than three days for laser scanning appear to be achievable.Direct nuclear laser excitation has come closer into reach within the past years, partly due to the development of free-electron-laser technology. Such ideas are typically dealing with the excitation of nuclear states in the energy range of at least a few keV or above [1,2]. However, there is one exceptional nuclear state known for the last 40 years with a significantly lower energy of presumably below 10 eV [3,4]. An excitation energy of (7.8 ± 0.5) eV, corresponding to (159 ± 11) nm wavelength or ∼ 1900 THz, is by today the most accepted value for the isomeric first excited state of 229 Th [5,6]. This state conceptionally allows for direct nuclear laser excitation using solid-state laser technology and was proposed for the development of a nuclear clock of extremely high stability, due to an expected high resilience against external influences and a radiative lifetime in the range of minutes to hours [7][8][9][10]. It is generally assumed that direct nuclear laser excitation of 229m Th requires a considerably improved knowledge of the isomeric transition energy (see e.g. Ref.[11] and references therein). The reasons are that, first, the present uncertainty in the knowledge of the isomeric energy value is still rather large. The currently best energy value of 7.8±0.5 eV leads to an energy range of at least 1 eV (corresponding to 2.4·1014 Hz) to be scanned when searching for the isomeric excitation. Second, the radiative lifetime of 229m Th was theoretically predicted to be in the range of hours [12][13][14], leading to long required detection times when searching for a radiative decay channel. This has led to the assumption that the required time for laserbased scanning of the large energy range of 1 eV would be prohibitively long. In order to shorten the required scanning times, there are worldwide efforts ongoing to decrease the uncertainty of the transition energy, which would bring the isomeric state into realistic reach of direct laser excitation (see e.g. Refs. [15-18]). A recent review is found in Ref. [11].Here we propose a different approach, which allows for a direct laser excitation of 229m Th without the requirement of an improved knowledge of the transition energy. As the requi...

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“…The design of the magnetic bottle spectrometer follows the concept that is used in Ref. [22]. In principle four components are needed to realize a magnetic bottle-type retarding field spectrometer: (i) a strong and inhomogeneous magnetic field (generated by a permanent magnet), (ii) a flight region with a weak and homogeneous magnetic field (generated by a solenoid coil), (iii) electrical retarding fields to block electrons, and (iv) an electron detector.…”

Section: Design Of the Magnetic Bottle Spectrometermentioning

confidence: 99%

Towards a precise determination of the excitation energy of the Thorium nuclear isomer using a magnetic bottle spectrometer

Wense

Amersdorffer

Arlt

et al. 2020

Nuclear Instruments and Methods in Physics Research Section B:

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229 Th is the only known nucleus with an excited state that offers the possibility for a direct laser excitation using existing laser technology. Its excitation energy has been measured indirectly to be 7.8(5) eV (≈160 nm). The energy and lifetime of the isomeric state make it the presently only suitable candidate for a nuclear optical clock, the uncertainty of the excitation energy is, however, still too large to allow for a direct laser excitation in a Paul trap. Therefore, a major goal during the past years has been an improved energy determination. One possible approach is to measure the kinetic energy of electrons which are emitted in the internal conversion decay of the first isomeric state in 229 Th. For this reason an electron spectrometer based on a magnetic bottle combined with electrical retarding fields has been built. Its design, as well as first test measurements are presented, which reveal a relative energy resolution of 3 % and thus enable to measure the electrons' expected kinetic energy to better than 0.1 eV. This is sufficiently precise to specify a laser system able to drive the nuclear clock transition in 229 Th.

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A highly sensitive electron spectrometer for crossed-beam collisional ionization: A retarding-type magnetic bottle analyzer and its application to collision-energy resolved Penning ionization electron spectroscopy

Cited by 31 publications

References 57 publications

Collision-energy-resolved Penning ionization electron spectroscopy of OCS with He*(23S) metastable atoms

Collision-energy-resolved Penning ionization electron spectroscopy of OCS with He*(23S) metastable atoms

A Laser Excitation Scheme for Th229m

Towards a precise determination of the excitation energy of the Thorium nuclear isomer using a magnetic bottle spectrometer

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