An ion trap is a combination of electric or magnetic fields that captures ion

Ion

An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

s in a region of a vacuum system or tube. Ion traps have a number of scientific uses such as mass spectrometery and trapping ions while the ion's quantum state is manipulated. The two most common types of ion traps are the Penning trap

Penning trap

Penning traps are devices for the storage of charged particles using a homogeneous static magnetic field and a spatially inhomogeneous static electric field. This kind of trap is particularly well suited to precision measurements of properties of ions and stable subatomic particles which have...

 and the Paul trap (quadrupole ion trap

Quadrupole ion trap

A quadrupole ion trap exists in both linear and 3D varieties and refers to an ion trap that uses constant DC and radio frequency oscillating AC electric fields to trap ions. It is commonly used as a component of a mass spectrometer...

).

When using ion traps for scientific studies of quantum state manipulation, the Paul trap is most often used. This work may lead to a trapped ion quantum computer and has already been used to create the world's most accurate atomic clocks.

An ion trap mass spectrometer may incorporate a Penning trap (Fourier transform ion cyclotron resonance

Fourier transform ion cyclotron resonance

Fourier transform ion cyclotron resonance mass spectrometry, also known as Fourier transform mass spectrometry, is a type of mass analyzer for determining the mass-to-charge ratio of ions based on the cyclotron frequency of the ions in a fixed magnetic field...

), Paul trap or the Kingdon trap

Kingdon trap

A Kingdon trap is a type of ion trap.In the Kingdon trap there is no potential minimum to store the ions; however, they are stored with a finite angular momentum about the central wire and the applied electric field in the device allows for the stability of the ion trajectories...

. The Orbitrap

Orbitrap

An orbitrap is a type of mass spectrometer invented by Alexander Makarov. It consists of an outer barrel-like electrode and a coaxial inner spindle-like electrode that form an electrostatic field with quadro-logarithmic potential distribution....

, introduced in 2005, is based on the Kingdon trap

Kingdon trap

A Kingdon trap is a type of ion trap.In the Kingdon trap there is no potential minimum to store the ions; however, they are stored with a finite angular momentum about the central wire and the applied electric field in the device allows for the stability of the ion trajectories...

. Other types of mass spectrometers may also use a linear quadrupole ion trap as a selective mass filter.

In an electron gun

Electron gun

An electron gun is an electrical component that produces an electron beam that has a precise kinetic energy and is most often used in television sets and computer displays which use cathode ray tube technology, as well as in other instruments, such as electron microscopes and particle...

 (a device emitting high-speed electrons, such as those in CRT

Cathode ray tube

The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...

s), an ion trap may be implemented above the cathode

Cathode

A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...

 (using an extra, positively-charged electrode between the cathode and the extraction electrode) to prevent its degradation by positive ions accelerated backward by the fields intended to pull electrons away from the cathode.

Penning ion trap

Penning trap is used for the storage of charged particles using a constant static magnetic field

Magnetic field

A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...

 and a spatially inhomogeneous static electric field

Electric field

In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...

.

Paul ion trap

A Paul trap uses static direct current

Direct current

Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...

 (DC) and radio frequency

Radio frequency

Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...

 (RF) oscillating electric field

Electric field

In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...

s to trap ions.

Kingdon trap

A Kingdon trap consists of a thin central wire and an outer cylindrical electrode. A static applied voltage results in a radial logarithmic potential between the electrodes.

Cathode ray tubes

Devices known as ion traps were used in early television receivers, prior to the introduction of aluminized CRT

Cathode ray tube

The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...

faces in approximately 1958. The ion trap must be delicately adjusted for maximum brightness. The purpose of these devices was to prevent ions from discoloring the phosphor screen.

External links

• VIAS Science Cartoons A cranky view of an ion trap...
• Paul trap