PHYS 1444 Section 002 Lecture #1brandta/teaching/salec/lectures/phys1444-lec1.pdf• My Research...

Tue. Jan. 18, 2011 PHYS 1444-002, Dr. Andrew Brandt 1

PHYS 1444 – Section 002

Lecture #1Tuesday Jan 18, 2007

Dr. Andrew Brandt

1. Syllabus and Introduction

2. Chapter 21

-Static Electricity and Charge Conservation

-Charges in Atom, Insulators and Conductors

&

Induced Charge

-Coulomb’s Law

Thanks to Dr. Yu for bringing this class into 21st Century!

Please turn off your cell-phones, pagers and laptops in class

Tue. Jan. 18, 2011 2

Who am I? • Name: Andrew Brandt (You can call me Dr. Brandt)

• Office: Rm 344, CPB (Physics and Chemistry Building)

• Extension: x2706, E-mail: [email protected]

• Education: B.S. Physics/Economics College of William and Mary 1985; Ph. D. 1992 UCLA

• My Research Area: High Energy Physics (HEP) aka Particle Physics– Collide particles (protons and protons or anti-protons) at energies equivalent

to ~100 Quadrillion degrees

– To understand• Fundamental constituents of matter

• Interactions or forces between the constituents

– A pure scientific research activity• No direct applications

• Indirect applications are myriad: electricity, nuclear power, lasers, radar, internet, I-pod, I-pad, Smart phones, all of technology

PHYS 1444-002, Dr. Andrew Brandt

mailto:[email protected]

Tue. Jan. 18, 2011 3

High Energy Physics

Structure of Matter

10-10m 10-14m 10-15m

<10-18m

10-9m

Matter Molecule Atom Nucleus

u

Quark

<10-19mprotons, neutrons,

mesons, etc.

top, bottom,

charm, strange,

up, down

Condensed matter/Nano-Science/Chemistry

Atomic Physics

Nuclear

Physics

Baryon(Hadron)

Electron(Lepton)

10-2m


Tue. Jan. 18, 2011 4

Fermilab Tevatron and LHC at CERN• Highest Energy proton-anti-

proton collider– Ecm=1.96 TeV (=6.3x10-7J/p

13M Joules on 10-4m2)

Equivalent to the kinetic energy of a 20t truck at a speed 80 mi/hr

Chicago

Tevatron p

p CDF

DØ

• World’s Highest Energy proton-proton collider– Ecm=14 TeV (=44x10-7J/p

1000M Joules on 10-4m2)

Equivalent to the kinetic energy of a 20t truck at a speed 212 mi/hr


Geneva

Tue. Jan. 18, 2011 5

DØ Detector: Run II

30’

50’

• Weighs 5000 tons

• Can inspect

3,000,000

collisions/second

• Records 50

collisions/second

• Records ~12.5M

Bytes/second

• Will record 2 Peta

bytes in the

current run.

• Has over a 100

million partsPHYS 1444-002, Dr. Andrew Brandt

Tue. Jan. 18, 2011 6

The Standard Model

• Assumes the following fundamental structure:

Directly

observed in

2000

Discovered in

1995

CDF+Dzero

(UTA a

member)


Tue. Jan. 18, 2011 7

High Energy Art

(an artist rendition

of a QCD dijet event

in the DØ Detector)


My Main Research Interests

• Physics with Forward Proton Detectors (detect

protons scattered at small angles)

• Fast timing detectors

• Triggering (selecting the events to write to tape):

at ATLAS must choose most interesting 300 out

of up to 40,000,000 events/sec

• Higgs Discovery (especially Beyond the

Standard Model Higgs)Tue. Jan. 18, 2011 8PHYS 1444-002, Dr. Andrew Brandt

One of the DØ Forward Proton Detectors built

at UTA and installed in the Tevatron tunnel

FermilabDØ

High-tech fan

Tevatron: World’s 2nd Highest Energy Collider

Tue. Jan. 18, 2011 9PHYS 1444-002, Dr. Andrew Brandt

Elastic Scattering Cross Section (FPD)


ATLAS Forward Protons: A (10) Picosecond

Window on the Higgs Boson

A picosecond is a trillionth of a second.

This door opens ~once a second, if it opened

every 10 picoseconds it would open a hundred

billion times in one second (100,000,000)

Light can travel 7 times around the earth in

one second but can only travel 3 mm in 10 psec

Yes, I know it’s a door, not a window!

11Tue. Jan. 18, 2011 PHYS 1444-002, Dr. Andrew Brandt

ATLAS Forward Proton Upgrade

AFP concept: adds new ATLAS sub-detectors at 220 and 420 m

upstream and downstream of central detector to precisely measure the scattered protons

to complement ATLAS discovery program.

These detectors are designed to run at a luminosity of 1034 cm-2s-1 and operate with

standard optics (need high luminosity for discovery physics)

AFP Components1) Rad-hard edgeless 3D silicon detectors with resolution ~10 m, 1 rad

2) Timing detectors to reject overlap background (SD+JJ+SD)

3) New Connection Cryostat at 420m

4) “Hamburg Beam Pipe” instead of Roman Pots

beam

p’

p’AFP Detector

LHC magnets

420 m 220 mH

Andrew Brandt, University of Texas, Arlington

12

10 picoseconds is design goal

(light travels 3mm in 10 psec!)

gives large factor of background rejection

Use time difference between protons to measure z-

vertex and compare with tracking z-vertex

measured with silicon detector

Pileup Background Rejection

Ex: Two protons from one interaction and two b-jets from another

Forward Proton Fast Timing

WHY?

How?

How Fast?


4x8 array of 5x5 mm2

fused silica bars

QUARTIC is Primary AFP Timing Detector

Multiple measurements with “modest” resolution simplifies requirements in all phases of system1) We have a readout solution for this option 2) We can have a several meter cable run to a lower radiation area where

electronics will be located3) Segmentation is natural for this detector4) Possible optimization with quartz fibers instead of bars

proton

Only need a 40 ps

measurement if you can do

it 16 times: 2 detectors with

8 bars each, with about 10

pe’s per bar

14

UTA, Alberta, Giessen,

Stonybrook (w/help from

Louvain and FNAL)

Tue. Jan. 18, 2011 PHYS 1444-002, Dr. Andrew Brandt

Photocathode

Dual MCP

Anode

Gain ~ 106

Photoelectron

V ~ 200V

V ~ 200V

V ~ 2000V

photon

+

+

MCP-PMT

Arradiance coating suppresses positive ion creation

(NSF SBIR Arradiance, UTA, Photonis)

+Ion Barrier keeps positive ions from

reaching photocathode

(developed by Nagoya with Hamamatsu

Use Photek Solar Blind photocathode or

similar (responds only to lower

wavelength/more robust)

Increase anode

voltage to reduce

crosstalk (UTA)

V ~ 500V

Gain <105

Run at low gain to

reduce integrated

charge (UTA)

Improve vacuum

Seal (Nagoya/

Hamamatsu)

A Long Life MCP-PMT e-


LeCroy Wavemaster 6 GHz Oscilloscope

Laser Box

Hamamatsu PLP-10 Laser Power Supply

PHYS 1444-002, Dr. Andrew Brandt16Tue. Jan. 18, 2011

laserlenses

filterMCP-PMT

beam splittermirror

Established with DOE

ADR, Texas ARP funds,

some supplemental support

for UG’s

- Ian Howley (Ph. D.

student), Ryan Hall (was

UG, now in UTA Ph. D.

program), both students

moving on soon…

- Monica Hew, Keith Gray,

James Bourbeau (UG)+…

Central Exclusive HiggsAFP concept: adds new ATLAS sub-detectors at 220 and 420 m

upstream and downstream of central detector to precisely measure the scattered

protons to complement ATLAS discovery program.

These detectors are designed to run at a luminosity of 1034 cm-2s-1 and operate

with standard optics (need high luminosity for discovery physics)

You might ask: “Why build a 14 TeV collider and have 99% of your energy taken away

by the protons, are you guys crazy or what??”

beam

p’

p’AFP Detector

LHC magnets

The answer is “or what”!—ATLAS is routinely losing energy

down the beam pipe, we just measure it accurately!!! The most important

Quantity is signal/background, not just signal

420 m 220 mH

17Tue. Jan. 18, 2011 PHYS 1444-002, Dr. Andrew Brandt

LeCroy Wavemaster 6 GHz Oscilloscope

Laser Box

Hamamatsu PLP-10 Laser Power Supply

Andrew Brandt UTA1810/14/2009

laserlenses

filterMCP-PMT

beam splittermirror

Established with DOE

ADR, Texas ARP funds,

some supplemental support

for UG’s

- Ian Howley (Ph. D.

student), Ryan Hall (was

UG, now in UTA Ph. D.

program), both students

moving on soon…

- Monica Hew, Keith Gray,

James Bourbeau (UG)+…

Tue. Jan. 18, 2011 19

Primary Web Page

http://www-hep.uta.edu/~brandta/teaching/sp2011/teaching.html


Tue. Jan. 18, 2011 20

Grading• Exams: 50%

– Best two of three exams (2 midterms + final)

– Comprehensive final

– Exams will be curved if necessary

– No makeup tests

• Homework: 20% (no late homework)

• Pop quizzes10% (no makeup quiz)

• Lab score: 20%


Tue. Jan. 18, 2011 21

Homework• Solving homework problems is the best (only?) way to

comprehend class material

• An electronic homework system has been setup

• Homework: will be done with Mastering Physics (can buy it with or

without text book (costs more but worth it!)

• http://www.masteringphysics.com/

• Course ID: MPBRANDT15116

• First “assignment” due Thurs.!!! It is optional (replace lowest HW),

but its content on using M. Phys. Is not optionsl


http://www.masteringphysics.com/

Tue. Jan. 18, 2011 22

Attendance and Class Style

• Attendance:

– is STRONGLY encouraged, but I will not take

attendence

• Class style:

– Lectures will be primarily on electronic media

• The lecture notes will be posted AFTER each class

– Will be mixed with traditional methods

– Active participation through questions and

discussion are STRONGLY encouraged


Tue. Jan. 18, 2011 23

Why Do Physics?

• To understand nature through experimental observations and measurements (Research)

• Establish limited number of fundamental laws, usually with mathematical expressions

• Explain and predict nature

⇒Theory and Experiment work hand-in-hand

⇒Theory generally works under restricted conditions

⇒Discrepancies between experimental measurements and theory are good for improvement of theory

⇒Modern society is based on technology derived from detailed understanding of physics

Exp.{

Theory {


Tue. Jan. 18, 2011 24

Why Do Physics Part Deux


http://www.aps.org/publications/apsnews/200911/physicsmajors.cfm

2008/2009 Graduates

1.7% unemployment

While engineering

starting salaries are

typically higher than

physicists (largely due

to biases by those who

take academic

positions), mid-career

salaries are virtually

identical 101k$ for

engineering 99k$ for

physics

Tue. Jan. 18, 2011 25

What Do Physicists Do?


Tue. Jan. 18, 2011 26

Brief History of Physics• AD 18th century:

– Newton’s Classical Mechanics: A theory of mechanics based on observations and measurements

• AD 19th Century:– Electricity, Magnetism, and Thermodynamics

• Late AD 19th and early 20th century (Modern Physics Era)– Einstein’s theory of relativity: Generalized theory of space, time, and energy

(mechanics)

– Quantum Mechanics: Theory of atomic phenomena (small distance scales)

• Physics has come very far, very fast, and is still progressing, yet we’ve got a long way to go – What is matter made of?

– How does matter get mass?

– How and why do particles interact with each other?

– How is universe created?


Tue. Jan. 18, 2011 27

Need for Standards and Units

• Three basic quantities for physical measurements– Length, Mass, and Time

• Need a language so that people can understand each other (How far is it to Chicago? 1000)

• Consistency is crucial for physical measurements– The same quantity measured by one person must be

comprehensible and reproducible by others

• A system of unit called SI (System International) established in 1960– Length in meters (m)

– Mass in kilo-grams (kg)

– Time in seconds (s)


Tue. Jan. 18, 2011 28

SI Base Quantities and Units

Quantity Unit Unit Abbrevation

Length Meter m

Time Second s

Mass Kilogram kg

Electric current Ampere A

Temperature Kelvin k

Amount of substance Mole mol

Luminous Intensity Candela cd

Tue. Jan. 18, 2011 29

Prefixes and their meanings

• deci (d): 10-1

• centi (c): 10-2

• milli (m): 10-3

• micro ( ): 10-6

• nano (n): 10-9

• pico (p): 10-12

• femto (f): 10-15

• atto (a): 10-18

• deca (da): 101

• hecto (h): 102

• kilo (k): 103

• mega (M): 106

• giga (G): 109

• tera (T): 1012

• peta (P): 1015

• exa (E): 1018

Impress your friends!

Tue. Jan. 18, 2011 30

Examples 1.3 and 1.4 for Unit Conversions

• Ex 1.3: A silicon chip has an

area of 1.25in2. Express this

in cm2.

21.25 in

22 cm 06.8cm 45.6 25.1

2

22

in 1

cm 45.6in 25.1

• Ex 1.4: Where the posted speed limit is 65 miles per hour (mi/h or mph), what is this

speed (a) in meters per second (m/s) and (b) kilometers per hour (km/h)?

1 mi=

65 mi/h

65 mi/h

(a)

(b)

21.25 in

22.54 cm

1 i

n

5280 ft 1609 m 1.609 km 12 in

1 ft

2.54 cm

1 in

1 m

100cm

65 mi 29.1 m/s 1609 m

1 mi

1

1 h

1 h

3600 s

65 mi 104 km/h 1.609 km

1 mi

1

1 h

Oops, what

about sig. figs.?

Tue. Jan. 18, 2011 31

Uncertainties

• Physical measurements have limited precision,

no matter how good they are, due to:

Number of measurements

Quality of instruments (meter stick vs micrometer)

Experience of the person doing measurements

Etc.

In many cases, uncertainties are more important and

difficult to estimate than the central (or mean) values

Statistical {

{Systematic


Tue. Jan. 18, 2011 32

Significant Figures

• Significant figures denote the precision of the

measured values

– Significant figures: non-zero numbers or zeros that are

not place-holders

• 34 has two significant digits; 34.2 has 3; 0.001 has one

because the 0’s before 1 are place holders, 34.100 has 5,

because the 0’s after 1 indicates that the numbers in these

digits are indeed 0’s.

• When there are many 0’s, use scientific notation:

– 31400000=3.14x107

– 0.00012=1.2x10-4


Tue. Jan. 18, 2011 33

Significant Figures

• Operational rules:– Addition or subtraction: Keep the smallest number of decimal

places in the result, independent of the number of significant digits: 34.001+120.1=154.1

– Multiplication or Division: Keep the number of significant figures of the operand with the least S.F. in the result: 34.001x120.1 = 4083, because the smallest number of significant figures is 4.

– For homework may need to get this right!


Tue. Jan. 18, 2011 34

Static Electricity; Electric Charge and

Its Conservation• Electricity is from Greek word elecktron=amber, a petrified

tree resin that attracts matter if rubbed

• Static Electricity: an amber effect

– An object becomes charged or “posses a net electric charge”

due to rubbing

– Example: Rub feet on carpet and zap your little sister

• Two types of electric charge

– Like charges repel while unlike charges attract

– Benjamin Franklin referred to the charge on a

glass rod as the positive, arbitrarily. Thus the

charge that attracts a glass rod is negative.

This convention is still used.PHYS 1444-002, Dr. Andrew Brandt

Tue. Jan. 18, 2011 35

Static Electricity; Electric Charge and

Its Conservation• Franklin argued that when a certain amount of charge is

produced on one body in a process, an equal amount of opposite type of charge is produced on another body.– The positive and negative are treated algebraically so that during any

process the net change in the amount of produced charge is 0.• When you comb your hair with a plastic comb, the comb acquires a negative

charge and the hair an equal amount of positive charge.

• This is the law of conservation of electric charge.– The net amount of electric charge produced in any process is

ZERO!!• If one object or one region of space acquires a positive charge, then an equal

amount of negative charge will be found in neighboring areas or objects.

• No violations have ever been observed.

• This conservation law is as firmly established as that of energy or momentum.


Tue. Jan. 18, 2011 36

Electric Charge in the Atom• It has been understood through the past century that an atom

consists of – A positively charged heavy core What is the name?

• This core is the nucleus and consists of neutrons and protons.

– Many negatively charged light particles surround the core What is the name of these light particles?

• These are called electrons

• How many of these?

• So what is the net electrical charge of an atom?– Zero!!! Electrically neutral!!!

• Can you explain what happens when a comb is rubbed on a towel?– Electrons from towel get transferred to the comb, making the comb

negatively charged while leaving positive ions on the towel.

– These charges eventually get neutralized primarily by water molecules in the air.

As many as the number of protons!!


Tue. Jan. 18, 2011 37

Insulators and Conductors• Let’s imagine two metal balls, one of which is charged

• What will happen if they are connected by – A metallic object?

• Charge is transferred, until the charge is evenly distributed

• These objects are called conductors of electricity.

– A wooden object?• No charge is transferred

• These objects are called nonconductors or insulators.

• Metals are generally good conductors whereas most other materials are insulators.– A third kind of materials called semi-conductors, like silicon or

germanium conduct only in certain conditions

• Atomically, conductors have loosely bound electrons while insulators have tightly bound electrons!


Tue. Jan. 18, 2011 38

Induced Charge

• When a positively charged metal object is brought

close to an uncharged metal object

– If the objects touch each other, the free electrons in the

neutral ones are attracted to the positively charged

object and some will pass over to it, leaving the neutral

object positively charged.

– If the objects get close, the free electrons in the neutral

object still move within the metal toward the charged

object leaving the opposite end of the object positively

charged.

• The charges have been “induced” in the opposite ends of the

object.


Tue. Jan. 18, 2011 39

Induced Charge

• We can induce a net charge on a metal object by connecting a wire to ground.– The object is “grounded” or “earthed”.

• Since it is so large and conducts, the Earth can give or accept charge. – The Earth acts as a reservoir for charge.

• If the negative charge is brought close to a neutral metal rod– Positive charges in the neutral rod will be attracted by the

negatively charged metal.

– The negative charges in the neutral metal will gather on the opposite side, transferring through the wire to the Earth.

– If the wire is cut, the metal bar has net positive charge.

• An electroscope is a device that can be used for measuring charge – How does this work?

ground


Tue. Jan. 18, 2011 40

Coulomb’s Law

• Charges exert force to each other. What factors affect the

magnitude of this force?

• Charles Coulomb figured this out in 1780’s.

• Coulomb found that the electrical force is

– Proportional to the product of the two charges

• If one of the charges is doubled, the force doubles.

• If both of the charges are doubled, the force quadruples.

– Inversely proportional to the square of the distances between them.

– Electric charge is a fundamental property of matter, just like mass.

• How would you put the above into a formula?


Tue. Jan. 18, 2011 41

• The value of the proportionality constant, k, in SI unit is

• Thus, if two 1C charges were placed 1m apart the force would be 9x109N.

1 2Q Q

Coulomb’s Law – The Formula

• Is Coulomb force a scalar quantity or a vector quantity? Unit?– A vector quantity. Newtons

• Direction of electric (Coulomb) force is always along the line joining the two objects.– If two charges have the same sign: forces are directed away from each other.

– If two charges are of opposite sign: forces are directed toward each other.

• Coulomb force is precise to 1 part in 1016.

• Unit of charge is called Coulomb, C, in SI.

F 1Q 1 2

2

Q QF k

r2r

2QFormula

9 2 28.988 10 N mk C

Tue. Jan. 18, 2011 42

Announcements

• Reading assignment: Read Ch. 21 by Thurs, Jan. 20

• Sign up for class in Mastering Physics and do first

“welcome” assignment

• Labs start week of Jan. 31

• Yesterday was MLK day (if you have 17 minutes, the

I have a Dream speech is worth a look:

http://www.youtube.com/watch?v=PbUtL_0vAJk )


http://www.youtube.com/watch?v=PbUtL_0vAJk

PHYS 1444 Section 002 Lecture #1brandta/teaching/salec/lectures/phys1444-lec1.pdf• My Research...

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