What is an Antiproton? Keith Gollwitzer Antiproton Source Department Accelerator Division Fermilab 8 August 2009

What is an Antiproton? Government issued Webster’s Dictionary: –“The antiparticle of the proton” Antiparticle definition “subatomic particle having the same mass, average lifetime, spin, magnitude of magnetic moment but opposite direction, magnitude of electric charge but opposite sign, opposite intrinsic parity” What about “Antimatter”? –“Matter made from antiparticles” What is a Pbar? –Shortened name for Antiproton based upon symbol used in physics –Over-line or bar above symbol means “anti” p for proton p for antiproton

So what are protons? –With neutrons form different atomic nuclei Simplest is Hydrogen nucleus of a single proton –Made up of quarks (up and down) Proton is uud Neutron is ddu Antiproton is uud –Antiquarks

Matter and Antimatter Matter –Plentiful and “free” by separating hydrogen components 13.6eV to ionize electron from proton Antimatter –Scarce in nature Created by cosmic rays interacting with the atmosphere. –The original “Fixed Target” experiment Positrons are by product of normal everyday radioactivity Particle & Antiparticle when they met --- annihilate –Who first informed us of this?

Where else Antimatter recently? Dan Brown’s Angels & Demons We will come back to this later Move back to reality and what Fermilab does

History: Particle Collisions Originally studied Cosmic Ray Particles Cosmic rays are energetic No human control of energy, type, when –Detection done at high altitudes –Discovered many types of particles that are not everyday matter Accelerators allow control of collisions –Allowed study of many new particles Some with masses greater than the initial particles

Fermilab Collisions Fixed Target –In the Fixed Target mode, ½ of the experiment is at rest. –The other ½ is moving at high energy. –There is a big “relativistic” penalty to be paid because of the conservation of momentum. Collider Mode –In the Collider mode, two particles of equal mass and energy travel directly at each other. –The total momentum of the system is zero, so there is no “relativistic” penalty to be paid. –Most of the energy goes directly into making new particles.

Particle Acceleration A charged particle will be accelerated by a voltage potential. –Opposite charges attract. One electron Volt (eV) is the energy gained by an electron (or any particle of unit charge) when it is accelerated through a potential of 1 Volt. + -

To Higher Energies Scientific Prefixes K (kilo) 1,000 M (mega) 1,000,000 G (giga) 1,000,000,000 T (tera) 1,000,000,000,000 TeVatron accelerates beam to nearly 1 trillion electron Volts Batteries are 1Volt per inch A trillion inches is 15.8 million miles

First Stage of the Acceleration Crockoft-Walton Accelerator –Can be thought of as a 750,000V DC voltage source. –The maximum voltage is limited by how much the air can “stand-off” before sparking.

Second Stage of Acceleration A linear accelerator (LINAC)

Drift Tube Linac

Synchrotrons The Fermilab Linac is 130 meters long and reaches an energy of 400 MeV (1 million Volts per foot) To get to 980 billion volts, a Linac would have to be –200 miles long at 1 million Volts per foot What about using the Linac over and over? –The drift tube spacing at the beginning of the Linac would be wrong for higher energy particles But a Synchrotron could be used! –Dipoles are used to bend particles –Quadrupoles are used to focus particles –RF cavities are used to accelerate particles

Dipole Magnets Dipole magnets are used to bend the particle’s path The magnet body confines or concentrates the magnetic field The pole faces shape the magnetic field

Quadrupole Magnets Quadrupoles are needed for focusing particles Not all the particles are on the “perfect” orbit. –If the particle is on the right orbit – don’t bend. –If the particle is on the inside – bend to the outside. –If the particle is on the outside – bend to the inside.

Pre-Acc First stage of acceleration Start with Hydrogen Bottle Final Energy = 750KeV

Linac Final Energy of 400MeV

Booster Ring Final Energy of 8GeV Uses combined function magnets

Main Injector Ring Final Energy of 150GeV 2 mile circumference Upper ring is the Recycler

Tevatron Ring Final Energy of 980GeV 4 mile circumference Uses cryogenic superconducting dipoles

Fixed Target Beam Lines Fixed Target program has run at 800GeV and currently at 120GeV Neutrino Program runs at two different energies 8GeV and 120GeV

Antiproton Source 120GeV protons from Main Injector hit (fixed) production target. Antiproton Source beam lines and rings capture and collect 8GeV pbars 8GeV pbars are sent to the rest of accelerator complex to be injected into the Tevatron for the collider program

The Antiproton Target Station 33 TargetLi Lens Pulsed Magnet 29 cm81cm Before After Nickel Alloy with air cooling through the copper disks

The Antiproton Target Station 33 TargetLi Lens Pulsed Magnet 29 cm81cm

“Hot” Beam The pbars leave the target at a wide range of energies, positions, and angles. This randomness is equivalent to temperature. The pbar beam is “hot” coming off the target. –This “hot” beam will have a difficult time fitting into a beam pipe of reasonable dimensions. –Also, this “hot” beam is very diffuse and not very “bright”. Bright beams are needed in the collider in order to increase the odds that the particles collide with particles in the other beam Stochastic cooling is a technique that is used to remove the randomness of the “hot” beam on a particle by particle basis.

Stochastic Cooling Stochastic cooling uses feedback A pickup electrode measures an “error” signal for a given pbar. –This error signal could be the pbar’s position or energy –The pickup signal can be extremely small, on the order of 1pW –The Debuncher pickups are cooled to 4 Kelvin to reduce the effect of thermal noise and 300 Kelvin “shine” This signal is processed and amplified –The gain of the Debuncher systems is about 150 dB The opposite of the error signal is applied to the pbar at the kicker –The kicker signal can be as large as 2 kW

Stochastic Cooling Pickups

Stacking Cycle - Debuncher Every 2.2 seconds –8 x (8 trillion) 120GeV protons onto target –Beam line transfers negatively charged 8GeV particles to the Debuncher Other particles decay or radiate away in a few turns Beam circulates every 1.6 microseconds – seconds –2.5 x 10 8 (250 million) 8GeV pbars circulate in the Debuncher Stochastic cooling reduces the phase space by a factor of ten –Transfer all pbars to the Accumulator

Stacking Cycle - Accumulator RF system decelerates from injection to deposition orbit Stochastic Cooling 2-4 GHz stacktail –Pushes and compresses beam into the core 2-4 & 4-8 GHz core momentum –Gathers beam from the stacktail 4-8 GHz transverse slotted waveguide pickups –Increase particle density by factor of 5000 –Factor of 3-5 decrease in both transverse phase space dimensions Cyan = After injection before RF capture Green = After RF is turned off

Accumulation rate of 2.5 x (250 billion) antiprotons per hour When reach 4 x (400 billion) pbars, transfer beam out of the Accumulator to the Main Injector into the Recycler Ring for storage until needed for the Tevatron collider program Most number of antiprotons that have been on site at Fermilab at one time (Accumulator, Recycler and Tevatron) –6 x (6 trillion) pbars 10pg = grams In 2008 produced –1400 trillion pbars (2.3ng) p p pp pp Total Antiprotons at Fermilab

Using Antiprotons Antiprotons are collected in Recycler Ring at 8GeV for a day Then antiprotons are sent in 36 batches to Main Injector to be accelerated to 150GeV Antiprotons are transferred to the Tevatron which already has 36 proton batches Both beams are accelerated to 980GeV

Tevatron Collider Two beams in one accelerator going in opposite directions! –Electrostatic separators keep beams on different helical orbits during acceleration Bring beams into collisions by collapsing helix orbits at desired interaction points –Middle of detectors

Angels & Demons + Antiprotons Page of “Facts” in a book of fiction Antimatter exists 0.25 grams of antimatter mixed with 0.25 grams of matter would produce an explosion equivalent Hiroshima (wipe out the Vatican)

Angels & Demons + Antiprotons Can easily produce 0.25 grams of antimatter –Fact: Fermilab is the world leader for producing antiprotons/antimatter –It would take 100 million years Can easily transport that much antimatter –Fact: Fermilab’s bottles are over 6 miles of rings It would cost a lot *2940 trillion $ ~ 420 x U.S. GNP

Antimatter Uses Scientific Studies –Laboratories use antimatter to collide with matter –Study why no antimatter today Applications –Example is Positron Emission Tomography (PET Scans) Not Spaceships Courtesy NIH

Safety You will be on tours in different areas –Including into the Antiproton Source tunnel No smoking, eating or drinking in the tunnel enclosure Please be careful on the stairs and walking –Edges of components and cables do stick out Tunnel is hot – 90 o F!

Today Enjoy your time at Fermilab Please take pictures Please ask questions Hope that you have learned a little about antiprotons, particle accelerators and what goes on at Fermilab