Download Particle accelerators and detectors

Particle accelerators and detectors -Short Answers
Question 1
Particle accelerators may be used to
accelerate protons. If the energy of the
accelerated protons is high enough
then, when these protons collide
with stationary protons, different
types of particles of large mass may be
produced
(a) Explain why high energies are
required to produce particles of large
mass
Question 1 Cont
(b)The diagram shows the basic structure of a cyclotron in which
protons are accelerated
Point on the diagram above to show the
(i) magnets and their polarity [1]
(ii)points where the alternating electric potential difference is
applied[1]
(c) Outline why the frequency of the alternating electric potential
difference is made equal to the frequency of orbit of the
protons
Question 1 Cont
The diagram shows the basic structure of a cyclotron in
which protons are accelerated
(c)
Outline why the frequency of the alternating
electric potential difference is made equal to the
frequency of orbit of the protons
Question 1 Cont
The diagram shows the basic structure of a cyclotron in
which protons are accelerated
(d) Explain the effect of the increasing energy of
the protons on their frequency of orbit and state
how this effect is dealt with in the cyclotron.
Question 1 Cont
The diagram shows the basic structure of a cyclotron in which
protons are accelerated
(e) Protons of much higher energy than those produced in a
cyclotron can be produced in a synchrotron. In a particular
experiment protons leave a synchroton with energy 28 GeV.
They enter a bubble chamber where some of them collide with
stationary protons. Deduce that the energy available to
produce other particles from these collisions is about 7 GeV.
Question 1
The diagram shows the basic structure of a cyclotron in
which protons are accelerated
(f) Suggest, based on the answer to (e) and
conservation of momentum, why it is better
to arrange for two protons of total energy 28 GeV,
moving in opposite directions, to collide.
Question 2
a)(i)Describe the operating principle of the
bubble chamber [2]
(ii)Outline how two particle properties or
characteristics are measured using a
bubble chamber [2]
(b)The proportional wire spark chamber has
now replaced the bubble chamber
Outline two advantages of this detector
compared to the bubble chamber [2]
Question 3
A drift tube accelerator has an alternating
potential difference of 50kV, with a
frequency of 10 MHz applied to a row of
tubular electrodes Calculate the length of
the drift tube if electrons are to arrive at
the right time to be accelerated in the
next gap
Question 4
• The synchrotron at Fermilab has a
diameter of 20 km Estimate the
magnetic flux density needed to move a
proton beam of 350 GeV
•
Question 5
A cyclotron is operated as an oscillator
frequency of 15 MHz and has a dee radius
of 050m
Calculate the magnetic flux density needed
to accelerate protons in the cyclotron
Determine the kinetic energy of the proton
in MeV
Question 6
Calculate the strength of a magnetic field
use in a cyclotron in which a deuteron
makes 15 x 107 revolutions per second
Question 7
Calculate the total energy and the
wavelength of a proton that has kinetic
energy of 30 GeV
Question 8
A drift tube accelerator has an
alternating potential difference of
30 kV, with a frequency of 15 MHz
applied to a tow of tubular
electrodes Calculate the lengths of
the first drift tube if electrons are
to arrive at the right time to be
accelerated in the next gap?
Question 9
At CERN, protons are injected into a 200m Diameter 28 GeV
synchrotron ring with an energy of 50 MeV The tube is
filled with protons which are injected with proton current
of 100 MA for 6 uS There are 14 acceleration point spaced
evenly around the ring with a potential difference between
the electrodes of each accelerator of 4 kV The final energy
of the proton is 28 GeV. If relavistive effects are ignored:
a) Calculate the speed of the protons at injection
b) Determine the time it takes to go around the ring at this
speed
c) Calculate the momentum of the proton at injection
d) Determine the number of protons that were injected
e) Deduce by how much the energy of proton increases in
each revolution of the synchrotron
f) Estimate the number of times a proton must go around the
accelerator to obtain its final maximum energy
Question 10
An ion gun in an evacuated container consists of 2 parallel
conducting plates separated by a distance of 20 cm A
potential difference of 50 kV is applied across the plates
Protons enter between the plates and drift with negligible
speed into a region between the plates The negative plate
has a small hole where protons can be ejected
(a)Calculate the electric field strength between the plates
(b)Determine the energy of the protons that are ejected
through the hole of the negative plate
(c) Deduce that the speed of the protons ejected through the
hole is approximately 31 x 10-6 ms’
(d) Describe why the apparatus is evacuated