Four Point Probe

What is it?

• Method to measure the sheet resistance of a material.

• Often in the form of a specific device.

• Compared with a typical 2 point probe, the 4PP does not have the problem of contact resistance (to the extent the 2PP does*) and it increases precision

Historical Background

• Designed by Frank Wenner in 1915

• Van der Pauw method was created by himself in 1958. Allowed for various geometries to be used. - Incredibly prevalent in the semiconductor industry

How does it work?

• Source current through two probes and measure voltage through other two.

• If utilizing a specific device, current is sourced on the outer prongs and the voltage drop is measured between the inner prongs.

• If utilizing the van Der Pauw method the points of contact in relation to the geometry of substrate are irrelevant. However, the voltage measuring contacts must be adjacent.

How to operate it?

• 4PP gives sheet resistance. If you wish for resistivity/conductivity (properties of the material itself), you must account for the geometry of the sample. You would multiply by thickness and a geometric correction factor.

• Van der Pauw method does not require a geometric correction factor assuming conditions are met for the sample.

• Sheet resistance is V/I

Electron Ion Collider

What is the Electron Ion Collider?

• The EIC has not yet been completely built nor operated, but Brookhaven National Lab is where the EIC will be built reusing some infrastructure from RHIC (relativistic heavy-ion collider)

• Eventually it will be a particle accelerator that collides electrons with protons or heavy nuclei

History?

• The EIC is the first of its kind, no other particle accelerator has directed electrons to collide with protons or heavy nuclei

• Thefuture discoveries of the EIC will be novel

What will the Electron Ion Collider do?

• Reveal arrangement of the quarks and gluons making up protons and neutrons of nuclei

• Offerinsight into the strong nuclear force and how it keeps quarks and gluons confined in matter

• Help our understanding of the evolution from quark- gluon plasma (QGP) to visible matter

• Measure how gluons, quarks, and quark-antiquark pairs contribute to proton spin

• Probes infrastructure of nuclear matter as it exists today (rather than when it existed at the beginning of the universe)

How does the Electron Ion Collider work?

• When the electron collides with the ion, the quarks that make up the proton or nucleus are scattered and hit different components of the detector.

• The patterns and traits of the particle products of the collision are analyzed by scientists to gain insight to the internal structure of ions (protons or nuclei).

How do you operate the EIC?

• The EIC will be operated by the EIC users group/ePIC

• Brookhaven National Lab and Jefferson Lab are designing the accelerators and detector for the EIC

Electron Emission

What is it?

• Electron emission is a phenomenon that involves the release of electrons from the surface of a material, usually metal.

• Occurs when electrons gain enough energy from an external source to overcome the attractive force of the positive nuclei inside the material.

• Can be induced by different sources of energy. Depending on the source of energy, electron emission can be classified into four main types: thermionic, photoelectric, field, and secondary electron emission

Historical background

• Thomson 1897: discovery of electrons

• Thomas Edison and John Ambrose Fleming studied the emission of electrons from heated filaments in vacuum tubes, created thermionic emission and the base of early electronic devices

• Heinrich Hertz: discovered photoelectric effect, studied in detail later by Albert Einstein

• Owen Richardson 1901: field emission first observed

• Secondary electron emission is experimented by different scientists

Applications:

• Thermionic emission: vacuum tube devices, cathode ray tubes vacuum diodes, triodes, magnetrons

• Field emission: field emission displays, electron microscopes, nanoelectronics, sensors

• Photoelectric: solar cells, photodetectors, photomultipliers, cameras

• Secondary electron emission: particle detectors, microscopy, thin film deposition

How it works:

• Thermionic emission

  • Occurs when a material is heated to a high temperature.

  • The heat energy increases the kinetic energy of the electrons in the material, enabling some of them to overcome the surface barrier and escape Intensity depends on temperature and work function of the material

• Field emission

  • Occurs when a strong electric field is applied to a material.

  • The electric field exerts a force on the electrons in the material, pulling some of them out of the surface Intensity of field emission depends on strength of electric field and work function of the material

• Photoelectric emission

  • Occurs when light of a certain frequency or wavelength shine on a material.

  • Light consists of photons, and when photons hit the surface of a material, they transfer their energy to some of the electrons in there, enabling them to overcome the surface barrier and escape.

  • Intensity depends on frequency, intensity of light and work function of the material

• Secondary electron emission

  • Occurs when a beam of high-energy particles, such as electrons or ions, strikes a material.

  • The impact transfers some of their kinetic energy to the electrons in the material, enabling them to overcome the surface barrier and escape Intensity depends on energy and angle of incidence of the particles and work function of the materia

Infrared Thermometer

What is it:

• A noncontact device that captures the temperature of a target objects surface.

Historical Background:

• 1800, Frederik William Herschel’s (Discovered Infrared radiation)

• 1963, Texas Instruments (forward-looking infrared system)

What its used for

• Healthcare Environments to measure patients’ temperatures

• Industrial environments to check for hot spots.

How it works

• Lens à Absorber à thermopile à Current displayed as temperature.

• Optical system(lens) that focuses infrared radiation à Detector (first goes to absorber which then goes into a thermopile) à electrical current that’s displayed as temperature.

How to operate it

• Turn on IR thermometer à turn on setting for laser à hold button to record objects temperature àtemperature is then displayed. (Might need to change emissivity depending on objects surface)

LHC:

What it is​:

• Largest (26 km) and the highest energy (up to 14 TeV) particle accelerator.

• Uses electromagnetic fields to accelerate particles close to speed of light (c) and direct highly energetic beams of hadrons on opposing circular paths such that they collide and the force of this collision produces elementary particles that can be studied to understand subatomic particles and the forces between them. 

Brief Historical Background​:

• Built by CERN, 50-175 m under the French-Swiss border over 1998 to 2008

• The tunnel was built between 1983-1988 to house the LEP collider 

  1. LHC was built which uses relatively much larger ions. 

• Built off several previous accelerators that feed into it; final part of the complex. 

• 2 major shutdowns where it went through extensive maintenance and upgrades. 

What it’s used for​

• Collide high energy particles so the byproduct of these collisions can be used to test various theories in particle physics. 

• The four major detectors are ATLAS, ALICE, CMS, and LHCb with their own objectives.

• Higgs particles which were theoretically predicted in 1964 and experimentally confirmed at LHC by the ATLAS and CMS detectors in 2012. 

How it works​

• Electric field: An oscillating current at radio frequency is introduced to the resonating cavity which amplifies this wave and creates strong electromagnetic fields which are powerful enough to accelerate particles nearly to c in bunches.

• Thousands of magnets are used to direct the beams in a circle and take measurements. 

• This requires copious amounts of energy so the entire system is cooled to ‑271.3°C to make superconductors using a distribution system of liquid helium to cool the system.

• Particles are accelerated before reaching the LHC; starting at an ion source → LINAC → proton synchrotron booster → proton synchrotron → super proton synchrotron. 

• At this point, the particles are at 0.999c which is so close to c that while the speed doesn’t increase much now, instead the increased energy now manifests as mass. 

• Finally, at LHC, they are split into 2 separate tubes kept at ultrahigh vacuum. 

• At this point, the particles can be accelerated up to 99.9999991% of c which translates to up to 6.5 TeV of energy per beam. 

• The particles collide at 4 crossings in the LHC producing up to 13 TeV of energy. 

• The energy from the collision turns to mostly known particles but also some exotic and extremely energetic particles as described by e = mc^2 which are captured by detectors. 

 How you operate it​:

• All of the controls and technical infrastructures are located in one building at the CERN control center from where the beams are fired. 

• After collisions, detectors record vast amounts of data which is processed and reconstructed which the researchers analyze to make new discoveries in particle physics.

Lasers

What is a Laser?

• A device that Produces a narrow beam of light.

• Stands for ‘Light Amlified by Stimulated Emission of Radiation’.

History of Lasers

• First introduced by Albert Einstein, by stimulated emission theory.

• Based off of MASER.

• Initially wasnt as popular as it is present day.

How Does a Laser Work?

• Works based off of two Principles:

  • 1) Stimulated Emission Theory

  • 2) Coherency of Light

• Excited Electrons are placed in a ‘gain medium’, such as glass or gases.

Uses and Operations of a Laser

• For Lasik eye surgery a light beam of UV wavelength is used.

• For Tattoo Removal the wavelength of light used depends on the color of the ink used for the tattoo.

• Nasais trying to replace radio frequency communications with optical communications, because the latter is more secure, lighter, and efficient

Molecular Beam Epitaxy:

What is Molecular Beam Epitaxy?

• Molecular Beam Epitaxy is a technique used in larger devices to develop thin films of unique crystals.

• This technique allows for great precision and control over the thickness, composition, and structure at the ATOMIC level of each crystal.

Brief Historical Background

• The groundwork for MBE was laid in the late 19th and early 20th centuries with the discovery of semiconductors and the development of semiconductor physics through early pioneers such as Sir William Thomson, who formulated the first comprehensive explanation of the behavior of electrical currents in metals and semiconductors.

• Then in the mid 20th century, scientists like Jan Czochralski, Percy Williams Bridgman, and Donald C. Stockbarger played crucial roles in the development of crystal growth methods during this time. They created the Czochralski method and the Bridgman-Stockbarger technique which allowed for the controlled growth of large single crystals of semiconductor materials.

• Now in the late 20th century, MBE as a technique emerged primarily through the pioneering work of J.R. Arthur and Alfred Y. Cho at Bell Laboratories in the United States. Companies like Riber and Veeco Instruments played significant roles in commercializing MBE systems, making them available to researchers and industries worldwide

What is MBE used for?

• MBE is mainly used for manufacturing of semiconductor devices.

• Its applications involve its use in CD players and advanced computer chips.

• Additionally, it is a major contributor to nanotechnology and quantum computing.

How does MBE work?

• The technique starts with a semiconductor material that is heated up to extreme temperatures.

• Then, through the use of effusion cells, also known as guns, precise beams of heated atoms or molecules are fired at the substrate.

• Each effusion cell shoots a different beam, and as the molecules land on the surface of the substrate, they begin to build up layer by layer at extremely slow speeds, roughly a few microns or even fractions of microns per hour.

• This is all done in an extremely clean, controlled environment as well as being kept in an ultra high vacuum.

Photodiode

What are Photodiodes?

• Photodiodes are semiconductors that convert light (infrared, visible, ultraviolet, x-rays, and gamma rays) into electricity.

• They contain a PN junction meaning that the semiconductor comprises a p-type and n-type semiconductor, separated by a small amount of space called the depletion layer. The depletion layer is where light detection takes place and where that light can be converted into either current or voltage.

Historical Background

• Early research into the photodiode first started in 1942.

• The first photodiode was invented in 1948 the photodiode by John Northrup Shive.

• The Photodide was formally introduced to the public in 1950 and the photodide continued to be improved through the 50s and 60s.

What are Photodiodes Used for?

• Photodiodes have many uses the simplest being solar cells and light detectors.

• Photodiodes are also commonly used in fire and smoke detectors and have many applications in the medical field.

HowDoPhotodiodes Work?

• Photodiodes work by taking in light and converting it to current and voltage.

• The light energy causes an electron-hole pair to form. The movement of the electron and electron-hole causes a current to be generated across the depletion layer.

How Do You Operate a Photodiode?

• A large part of operating a photodiode is determining the bias condition in which the photodiode should be placed. The most common bias condition for photodiodes is reverse bias.

• In reverse bias conditions or photoconductive mode, a positive voltage is applied to the n-type semiconductor and a negative to the p-type

RHIC

The purpose of the RHIC (relativistic Heavy ion collider) at Brookhaven National laboratory is to understand Quantum Chromodynamics by studying Quark-Gluon Plasma

The RHIC accelerates two beams of heavy ions such as gold and lead in opposite directions. At six intersections, the beams collide, creating conditions like the universe's beginning.

The major detectors at RHIC are STAR (Solenoidal Tracker At RHIC) and sPHENIX (Small Polarized High-Energy Nuclear Interaction eXperiment). STAR is a more general-purpose detector while sPHENIX is a specialized detector for studying quark gluon plasma.

Superconductor

What are Superconductors

• Specific material cooled to critical temperatures

• Perfect conductivity- no resistance or energy loss

• Diamagnetic levitation- opposition magnetic field causing magnetic fields to be suspended

History of Superconductors

• Discovered in 1911 by Kamerlingh-Onnes who pioneered low temperature physics

• In 1933, diamagnetic forces in superconductor by Meissner and Ochsenfeld

• In 1935, London and Heinz derived formulas for superconductivity using Ohm’s law

• In 1950, two labs discover isotope effect where critical temperature is inversely proportional to the root mass.

What Superconductors do

● MRI

● 4-bit microchips, which are 500x faster than todays 32-bit

● Cables

● Generators

● MagLev trains

● Accelerators

How Superconductors work

● Isotope effect- critical temperature is inversely proportional to the root mass due to the spring like nature of solid lattices

● Lattice vibrations- solid lattice structure vibrating and throwing electrons

● Energy gao- gap of energy in between 2 energy levels

● Pauli Exclusion Principal- electrons can go in certain orbits

● Fermi energy- outer electrons have more energy than inner

● Condensed velocity space- a state where electrons in a space all move at the same velocity

Vaccum Pumps

What is a Vacuum Pump?

• Vacuum pumps are mechanical devices that act to reduce the pressure inside a sealed chamber to allow gas and air molecules to be pumped out; they create a low pressure environment by extracting gas or air from a system.

• A vacuum pump often utilizes fluid flow (viscous pumping), where a high-pressure system will naturally flow to a low-pressure system. There are three types of vacuum pumps; positive displacement, momentum, and entrapment pumps; positive displacement are most common in lab settings (create low vacuums).

History of Vacuum Pumps

• Otto von Guericke (1602-1686) invented the first true vacuum pump that could remove the air from two metal hemispheres to create a vacuum strong enough to stop a team of horses from pulling it apart.

• Heinrich Geissler (1814-1879) invented the Geissler tube, a sealed glass tube containing near vacuum, which showed passage of electricity through it and led to discovery of electron.

What are Vacuum Pumps used for?

• Regarding positive displacement pumps (most common in lab settings), vacuum pumps can be used for refrigeration, air conditioning, and lab equipment maintenance.

• They can collect gas samples from test chambers, push aspiration or filtration of suspended samples in a chamber, and improve sensitivity of a lab instrument by evaluating the molecules in an air sample.

How do Vacuum pumps work?

• Positive displacement vacuum pumps can generate a partial vacuum by increasing the volume of a container; a compartment of the vacuum can be repeatedly closed off, exhausted, and expanded to evacuate a chamber.

• These pumps expand a small, sealed cavity, which pushes air from the chamber into the cavity, which is then sealed from the chamber, opened to the atmosphere, and compressed back to small size.

How to use a Vacuum Pump

1. Start the pump by activating motor

2. Monitor the pressure on vacuum pressure gauge

3. Monitor pump’s performance and temperature

4. Shut down according to manufacturer’s instructionsElias Gettemy, Vacuum Pump Extraordinaire broom broom vrrrr