ISOLTRAP experiment

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Isotope Separator On Line Device
(ISOLDE)
List of ISOLDE experimental setups
COLLAPS, CRIS, EC-SLI, IDS, ISS, ISOLTRAP, LUCRECIA, Miniball, MIRACLS, SEC, VITO, WISArD
Other facilities
MEDICIS Medical Isotopes Collected from ISOLDE
508Solid State Physics Laboratory
ISOLTRAP experiment in the ISOLDE facility at CERN ISOLTRAP 001.png
ISOLTRAP experiment in the ISOLDE facility at CERN

The high-precision mass spectrometer ISOLTRAP experiment is a permanent experimental setup located at the ISOLDE facility at CERN. The purpose of the experiment is to make precision mass measurements using the time-of-flight (ToF) detection technique. [1] Studying nuclides and probing nuclear structure gives insight into various areas of physics, including astrophysics. [2]

Contents

Background

Mass spectrometry is a technique to determine the mass-to-charge ratio of ions. For a radioactive ion beam, there may be many radionuclides present within the beam and mass separation is needed to isolate a specific ion for measurements.

An ion trap uses electric and magnetic fields to capture charged particles in a system. There are multiple types of ion traps using various mechanisms, including the Penning trap. A Penning trap uses a uniform magnetic field and a quadrupole electric field to confine the particle radially and axially respectively. [3]

Experimental setup

ISOLTRAP experimental setup area at ISOLDE ISOLTRAP area.jpg
ISOLTRAP experimental setup area at ISOLDE

The ISOLTRAP experiment is a high-precision mass spectrometer/separator, consisting of four ion traps. These include a radio-frequency quadrupole (RFQ) trap, a multi-reflection time-of-flight (MR-ToF) mass spectrometer, and two Penning traps. [4]

The RFQ trap is used convert the radioactive ion beam delivered by the ISOLDE facility into low-energy ion pulses, before it is injected into the MR-ToF mass spectrometer. [5] It does this by electrostatically decelerating the ions and then passing them through a buffer-gas-filled environment. [6] The radio-frequency creates an oscillating electric field which confines the ions to a thin line. The ions are guided towards the trapping region by a potential, where they interact with the buffer gas and the energy spread of ions is reduced. [7] This forms a small cloud of ions which is then ejected as a bunch out of the trapping region and transported to the MR-ToF. [8]

Ion detector (left) and MR-ToF mass spectrometer (right) ISOLTRAP setup.jpg
Ion detector (left) and MR-ToF mass spectrometer (right)

The MR-ToF mass spectrometer/separator injects and ejects ions, using a switched cavity, and reflects them between two electrostatic mirror sets to increase their flight path. [9] This gives a large resolving power for a short trapping time, and therefore efficient isobaric separation can be performed. [10] The ToF of the ion is measured by an electron multiplier particle detector and can be used to determine the corresponding mass. [11] [12]

The two Penning traps following the MR-ToF are the preparation Penning trap and the precision Penning trap. [4] The preparation Penning trap, a large cylindrical trap, is placed in the uniform field of a superconducting magnet. [13] [12] The ions are captured and, with high-selectivity, cooled by mass. [14] Mass measurements are made by the precision Penning trap, which uses a radio frequency field to drive cyclotron motion of the ions. The ions are then ejected from the trap and drift to the non-uniform outside (fringe) field of the magnet to an ion detector. Ions that were at resonance due to the radio frequency field reach the detector faster than the others and the ToF can be determined. [14] [15]

Results

Doubly magic Nickel from one proton away Copper-79.jpg
Doubly magic Nickel from one proton away

Since the start of its operation, ISOLTRAP has measured the masses of hundreds of short-lived radioactive nuclei. [16] [17] Initially, the experimental setup consisted of just two Penning traps but since the MR-ToF was installed in 2011, the most exotic nuclides that can be detected are now measured at ISOLTRAP. [4]

One purpose of the ISOLTRAP experimental results is to confirm doubly magic isotopes. Doubly magic isotopes are those that have both numbers of protons and neutrons equal to magic numbers. They are very stable against decay. Results from ISOLTRAP have confirmed that nickel-78 is doubly magic by studying its neighbour, copper-79. [18] [19]

Related Research Articles

<span class="mw-page-title-main">Antimatter</span> Material composed of antiparticles of the corresponding particles of ordinary matter

In modern physics, antimatter is defined as matter composed of the antiparticles of the corresponding particles in "ordinary" matter, and can be thought of as matter with reversed charge, parity, and time, known as CPT reversal. Antimatter occurs in natural processes like cosmic ray collisions and some types of radioactive decay, but only a tiny fraction of these have successfully been bound together in experiments to form antiatoms. Minuscule numbers of antiparticles can be generated at particle accelerators; however, total artificial production has been only a few nanograms. No macroscopic amount of antimatter has ever been assembled due to the extreme cost and difficulty of production and handling. Nonetheless, antimatter is an essential component of widely available applications related to beta decay, such as positron emission tomography, radiation therapy, and industrial imaging.

<span class="mw-page-title-main">Mass spectrometry</span> Analytical technique based on determining mass to charge ratio of ions

Mass spectrometry (MS), also called mass spec, is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a mass spectrum, a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures.

<span class="mw-page-title-main">Ion source</span> Device that creates charged atoms and molecules (ions)

An ion source is a device that creates atomic and molecular ions. Ion sources are used to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines.

<span class="mw-page-title-main">Penning trap</span> Device for storing charged particles

A Penning trap is a device for the storage of charged particles using a homogeneous magnetic field and a quadrupole electric field. It is mostly found in the physical sciences and related fields of study as a tool for precision measurements of properties of ions and stable subatomic particles, like for example mass, fission yields and isomeric yield ratios. One initial object of study were the so-called geonium atoms, which represent a way to measure the electron magnetic moment by storing a single electron. These traps have been used in the physical realization of quantum computation and quantum information processing by trapping qubits. Penning traps are in use in many laboratories worldwide, including CERN, to store and investigate anti-particles such as antiprotons. The main advantages of Penning traps are the potentially long storage times and the existence of a multitude of techniques to manipulate and non-destructively detect the stored particles. This makes Penning traps versatile tools for the investigation of stored particles, but also for their selection, preparation or mere storage.

<span class="mw-page-title-main">Halo nucleus</span> Core atomic nucleus surrounded by orbiting protons or neutrons

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<span class="mw-page-title-main">Ion trap</span> Device for trapping charged particles

An ion trap is a combination of electric and/or magnetic fields used to capture charged particles — known as ions — often in a system isolated from an external environment. Atomic and molecular ion traps have a number of applications in physics and chemistry such as precision mass spectrometry, improved atomic frequency standards, and quantum computing. In comparison to neutral atom traps, ion traps have deeper trapping potentials that do not depend on the internal electronic structure of a trapped ion. This makes ion traps more suitable for the study of light interactions with single atomic systems. The two most popular types of ion traps are the Penning trap, which forms a potential via a combination of static electric and magnetic fields, and the Paul trap which forms a potential via a combination of static and oscillating electric fields.

<span class="mw-page-title-main">ISOLDE</span> Physics facility at CERN

The ISOLDE Radioactive Ion Beam Facility, is an on-line isotope separator facility located at the centre of the CERN accelerator complex on the Franco-Swiss border. Created in 1964, the ISOLDE facility started delivering radioactive ion beams (RIBs) to users in 1967. Originally located at the Synchro-Cyclotron (SC) accelerator, the facility has been upgraded several times most notably in 1992 when the whole facility was moved to be connected to CERN's ProtonSynchroton Booster (PSB). ISOLDE is currently the longest-running facility in operation at CERN, with continuous developments of the facility and its experiments keeping ISOLDE at the forefront of science with RIBs. ISOLDE benefits a wide range of physics communities with applications covering nuclear, atomic, molecular and solid-state physics, but also biophysics and astrophysics, as well as high-precision experiments looking for physics beyond the Standard Model. The facility is operated by the ISOLDE Collaboration, comprising CERN and sixteen (mostly) European countries. As of 2019, close to 1,000 experimentalists around the world are coming to ISOLDE to perform typically 50 different experiments per year.

<span class="mw-page-title-main">Quadrupole ion trap</span> Type of apparatus for isolating charged particles

In experimental physics, a quadrupole ion trap or paul trap is a type of ion trap that uses dynamic electric fields to trap charged particles. They are also called radio frequency (RF) traps or Paul traps in honor of Wolfgang Paul, who invented the device and shared the Nobel Prize in Physics in 1989 for this work. It is used as a component of a mass spectrometer or a trapped ion quantum computer.

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<span class="mw-page-title-main">MIRACLS experiment</span>

The Multi Ion Reflection Apparatus for Colinear Laser Spectroscopy (MIRACLS) is a permanent experiment setup being constructed at the ISOLDE facility at CERN. The purpose of the experiment is to measure properties of exotic radioisotopes, from precise measurements of their hyperfine structure. MIRACLS will use laser spectroscopy for measurements, aiming to increase the sensitivity of the technique by trapping ion bunches in an ion trap.

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The Weak Interaction Studies with 32Ar Decay (WISArD) experiment is a permanent experimental setup located in the ISOLDE facility, at CERN. The purpose of the experiment is to investigate the weak interaction by looking for beta-delayed protons emitted from a nucleus. In the absence of online isotope production during Long Shutdown 2, the experimental setup has also been used to measure the shape of the beta energy spectrum. A goal of the experiment is to search for physics beyond the Standard Model (SM) by expanding the existing limits on currents in the weak interaction.

References

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