Periodic Reporting for period 2 - FunI (Revealing Fundamental Interactions and their Symmetries at the highest Precision and the lowest Energies)
Okres sprawozdawczy: 2020-11-01 do 2022-04-30
Within the project FunI tests of fundamental interactions and their symmetries determining the basic structure of the universe shall be performed with improved precision. Predictions of the underlying theory, e.g. bound-state quantum electrodynamics, will be tested with so far unprecedented precision. The improvement of these tests beyond the present level of accuracy represents a significant challenge for modern measurement techniques. This requires novel extensive experimental developments like, e.g. new manipulation, cooling, storage, and production techniques for the studied particles.
There are still a number of open question that can not be answered within our Standard Model predictions, among others why neutrinos have a mass. To answer these questions and to search for physics beyond the Standard Model is of fundamental importance for our society. Of course also knowedge and technology transfer is of importance, as done by a close collaboration with the Physikalische Technische Bundesanstalt in Braunschweig.
The overall objectives are to perform the most stringent tests of fundamental symmetries like charge-parity-time reversal symmetry (CPT theorem) with (anti)protons or of the energy-mass equivalence principle as well as tests of interactions like quantum electrodynamics in strong fields by using highly charged ions. This will enable us to set new limits on Standard Model predictions or even to reveal their failures.
There are still a number of open question that can not be answered within our Standard Model predictions, among others why neutrinos have a mass. To answer these questions and to search for physics beyond the Standard Model is of fundamental importance for our society. Of course also knowedge and technology transfer is of importance, as done by a close collaboration with the Physikalische Technische Bundesanstalt in Braunschweig.
The overall objectives are to perform the most stringent tests of fundamental symmetries like charge-parity-time reversal symmetry (CPT theorem) with (anti)protons or of the energy-mass equivalence principle as well as tests of interactions like quantum electrodynamics in strong fields by using highly charged ions. This will enable us to set new limits on Standard Model predictions or even to reveal their failures.
WP1a: [Mths 1-24]
Many Penning-trap mass spectrometers worldwide aim for mass measurements on exotic nuclides, which are only available in minute quantities in the order of 1E14 atoms and below. This is also the case for the measurements proposed in WP2a and 2b of the FunI project. In order to have an efficient injection of the rare species into an electron beam ion trap (EBIT) for charge breeding, a metallic wire probe has been developed. We have demonstrated a steady production of highly charged ions (HCI) of the stable isotope 165Ho from samples of only 1E12 atoms (∼300 pg) in charge states up to 45+ [Ch. Schweiger et al., Rev. Sci. Instrum. 90, 123201 (2019)].
WP1b: [Mths 1-36]
Efficient cooling and coupling of trapped charged particles is essential in fundamental physics experiments, high-precision metrology, and quantum technology. Until now, coupling techniques of ions and sympathetic cooling have required close range Coulomb interactions. Therefore, there is a sustained desire to extend laser cooling techniques to particles in macroscopically separated traps. We have demonstrated within this WP for the first time the coupling between a proton as well as a highly charged ion and a cloud of laser-cooled beryllium ions stored in two spatially separated traps of an advanced Penning-trap system, which exchange energy through a common superconducting LC circuit [B. Tu et al., Adv. Quantum Techn. 2100029 (2021) and M. Bohman et al., Nature 596, 514 (2021)]. Still to be shown in this working package WP1b is the final temperature of the species to be cooled.
WP2a: [Mths 26-60]
The proposed test of special relativity requires high-precision mass measurements on 35,36Cl, i.e. on light mass species. To demonstrate a relative mass precision at the 1E-11 level and better it is mandatory to perform systematic studies on light ion species, like carbon, oxygen and neon. The measurements on neon have been completed recently and data analysis is ongoing.
WP2b: [Mths 1-60]
The new Penning-trap experiment named PENTATRAP aims on the ultra-high precision determination of the masses of long-lived as well as stable species for fundamental studies. In order to check for unknown systematic uncertainties well-known medium heavy nuclides like the isotopic chain of Xe have been measured. Relative mass uncertainties as low as 1E-11 have been demonstrated [A. Rischka et al., Phys. Rev. Lett. 124, 113001 (2020)].
One of the difficulties in the measurement of the QEC-value of the electron capture decay of 163Ho to 163Dy is the possible appearance of long-lived low-lying excited electronic states, which would result in a wrongly determination of the Q-value or an increased systematic uncertainty. In order to see how well such long-lived low-lying electronic states can be resolved, demonstration measurements have been carried out in the Re-Os system [R.X. Schüssler et al. Nature 581, 42-46 (2020)]. In parallel systematic high-resolution and low-background studies on the 163Ho spectrum have been carried out [C. Velte et al., Eur. Phys. J. C 79, 1026 (2019)]. To reduce systematic uncertainties new ion control electronics has been developed [J. Herkenhoff et al., Rev. Sci. Instrum. 92, 103201 (2021)]. First mass measurements on 163Ho vs. 163Dy have been recently completed and the data is under analysis.
WP3a: [Mths 1-60]
At ALPHATRAP, an apparatus for high-precision g-factor measurements of the bound electron in highly charged (hydrogen- and boron-like) heavy ions, systems like 208Pb81+ or 208Pb77+ will be addressed. To that end we are developing a so-called hyper-EBIT, able to produce up to hydrogen like lead. First results have already been obtained, e.g. charge breeding of hydrogen like 120Zn49+ (Z=50) was demonstrated. In this second reporting period g-factor measurements on H-like, Li-Like and Ne-like 120Zn49+ have been completed, provided the most stringent test of BS-QED so far. The publication is under preparation. This WP is a bit behind schedule since the postdoc involved could only be hired nine months after the start of the project and a major upgrade of the electron beam ion trap for the production of heavy highly charged ions is required.
WP3b: [Mths 1-60]
Precise comparisons of the fundamental properties of matter and antimatter provide stringent tests of CPT symmetry, the most fundamental symmetry of the Standard Model of particle physics. Tests at the level of 1E-9 by comparing the g-factors of the proton and the antiproton have already been performed in the past. As a first step a factor of 5 in improvement is aimed for by using a novel and recently developed phase detection method for the induced image currents. Although major progress has been achieved, this project is behind schedule since a postdoc could only be hired 18 months after the start. The main problem is still the COVID-19 situation.
Many Penning-trap mass spectrometers worldwide aim for mass measurements on exotic nuclides, which are only available in minute quantities in the order of 1E14 atoms and below. This is also the case for the measurements proposed in WP2a and 2b of the FunI project. In order to have an efficient injection of the rare species into an electron beam ion trap (EBIT) for charge breeding, a metallic wire probe has been developed. We have demonstrated a steady production of highly charged ions (HCI) of the stable isotope 165Ho from samples of only 1E12 atoms (∼300 pg) in charge states up to 45+ [Ch. Schweiger et al., Rev. Sci. Instrum. 90, 123201 (2019)].
WP1b: [Mths 1-36]
Efficient cooling and coupling of trapped charged particles is essential in fundamental physics experiments, high-precision metrology, and quantum technology. Until now, coupling techniques of ions and sympathetic cooling have required close range Coulomb interactions. Therefore, there is a sustained desire to extend laser cooling techniques to particles in macroscopically separated traps. We have demonstrated within this WP for the first time the coupling between a proton as well as a highly charged ion and a cloud of laser-cooled beryllium ions stored in two spatially separated traps of an advanced Penning-trap system, which exchange energy through a common superconducting LC circuit [B. Tu et al., Adv. Quantum Techn. 2100029 (2021) and M. Bohman et al., Nature 596, 514 (2021)]. Still to be shown in this working package WP1b is the final temperature of the species to be cooled.
WP2a: [Mths 26-60]
The proposed test of special relativity requires high-precision mass measurements on 35,36Cl, i.e. on light mass species. To demonstrate a relative mass precision at the 1E-11 level and better it is mandatory to perform systematic studies on light ion species, like carbon, oxygen and neon. The measurements on neon have been completed recently and data analysis is ongoing.
WP2b: [Mths 1-60]
The new Penning-trap experiment named PENTATRAP aims on the ultra-high precision determination of the masses of long-lived as well as stable species for fundamental studies. In order to check for unknown systematic uncertainties well-known medium heavy nuclides like the isotopic chain of Xe have been measured. Relative mass uncertainties as low as 1E-11 have been demonstrated [A. Rischka et al., Phys. Rev. Lett. 124, 113001 (2020)].
One of the difficulties in the measurement of the QEC-value of the electron capture decay of 163Ho to 163Dy is the possible appearance of long-lived low-lying excited electronic states, which would result in a wrongly determination of the Q-value or an increased systematic uncertainty. In order to see how well such long-lived low-lying electronic states can be resolved, demonstration measurements have been carried out in the Re-Os system [R.X. Schüssler et al. Nature 581, 42-46 (2020)]. In parallel systematic high-resolution and low-background studies on the 163Ho spectrum have been carried out [C. Velte et al., Eur. Phys. J. C 79, 1026 (2019)]. To reduce systematic uncertainties new ion control electronics has been developed [J. Herkenhoff et al., Rev. Sci. Instrum. 92, 103201 (2021)]. First mass measurements on 163Ho vs. 163Dy have been recently completed and the data is under analysis.
WP3a: [Mths 1-60]
At ALPHATRAP, an apparatus for high-precision g-factor measurements of the bound electron in highly charged (hydrogen- and boron-like) heavy ions, systems like 208Pb81+ or 208Pb77+ will be addressed. To that end we are developing a so-called hyper-EBIT, able to produce up to hydrogen like lead. First results have already been obtained, e.g. charge breeding of hydrogen like 120Zn49+ (Z=50) was demonstrated. In this second reporting period g-factor measurements on H-like, Li-Like and Ne-like 120Zn49+ have been completed, provided the most stringent test of BS-QED so far. The publication is under preparation. This WP is a bit behind schedule since the postdoc involved could only be hired nine months after the start of the project and a major upgrade of the electron beam ion trap for the production of heavy highly charged ions is required.
WP3b: [Mths 1-60]
Precise comparisons of the fundamental properties of matter and antimatter provide stringent tests of CPT symmetry, the most fundamental symmetry of the Standard Model of particle physics. Tests at the level of 1E-9 by comparing the g-factors of the proton and the antiproton have already been performed in the past. As a first step a factor of 5 in improvement is aimed for by using a novel and recently developed phase detection method for the induced image currents. Although major progress has been achieved, this project is behind schedule since a postdoc could only be hired 18 months after the start. The main problem is still the COVID-19 situation.
First precision mass measurements on stable Xe isotopes with relative uncertainties as low as 1E-11 with PENATRAP have demonstrated the amazing capabilities of the PENTATRAP mass spectrometer. Furthermore, for the first time long-loved low-lying excited electronic states in highly charged ions could be observed and resolved by Penning trap mass spectrometry. This has been a major milestone for the precise determination of the end point energy in the electron capture decay of 163Ho. Until the end of the project the present best Q-values of the 163Ho decay shall be improved by a factor of 10. Furthermore, the most stringent test of E=mc² shall be carried out. To apply our experimental techniques to measure the proton and antiproton magnetic moment and to perform a stringent test of CPT symmetry on the baryonic sector, an upgrade of BASE - Baryon Antibaryon Symmetry Experiment is presently ongoing, among others the possibility to sympathetically laser cool the particles is implemented. Until the end of the project the magnetic moments of the proton and the antiproton shalle be improved by a factor of 5 and 10, respectively.