changing the relative positions (phases) of adjacent rows of magnets—a “row scan.”
In the case of the EPU on ALS beamline 4.0.2, the polarization can be changed from
left to right circular polarization in a few seconds, and the peak energy can be varied
as quickly as the monochromator scans [54,55].
A final note—why are the frames for these IDs so huge? It turns out that when the
gaps are closed down, the magnetic forces between the jaws are enormous—several
thousand Newtons per meter of length. For a 3 meter insertion device, this translates
to over 10,000 Newtons or over a ton of force. No wonder the overall assemblies can
weigh ~9000 kg!
2.6 Suggested Exercises
1. What is the bend radius for a dipole magnet with a field of 2 Tesla for an electron
beam with an energy of 2 GeV?
2. What is the approximate focal length of a quadrupole doublet where the field
gradient for each quadrupole is 10 Tesla/m, the length of the magnets is 0.3 m, the
separation between the magnets is 3 m, and the beam energy is 2 GeV?
3. Using approximate values from Fig. 2.10, calculate the minimum and maximum
horizontal beam sizes for the Sirius storage ring. Assume the horizontal emittance
is 0.28 nm rad.
4. The MAX-IV ring has a circumference of 528 m and runs with a microwave
frequency of 99.931 MHz. Calculate the harmonic number h.
5. Consider a Nd 2 Fe 14 B magnet PPM insertion device with rectangular blocks, an
undulator period of 68.3 mm, and a minimum gap of 23.82 mm. If we assume that
the magnet remanent field was 1.26 T, what would the maximum field be at the
device center?
6. Compare a SmCo 5 hybrid magnet undulator with a remanent field B r ¼ 0.9 T with
a Nd 2 Fe 14 B hybrid with a remanent field B r ¼ 1.3 T. In both cases, assume high
permeability (vanadium-permendur) alloy pole pieces. Calculate the fields at a
1.2 cm gap if the undulator magnetic period is 7.00 cm. (You will have to research
the proper formula for the latter device.)
7. One sometimes reads that high-energy electrons are at the front of the bunch,
because they have a higher velocity. Calculate the difference in transit times for
electrons of energy 2.9 and 3.1 GeV, if they were to travel along a perfect circle
with a circumference of 500 m.
2.7 Reference Books and Review Articles
1. Particle Accelerator Physics—Basic Principles and Linear Beam Dynamics;
H. Wiedemann, Springer-Verlag: Heidelberg, fourth Edition, 2015, ISBN
978-3-662-02903-9—in-depth treatment of accelerator and storage rings.
36
2 The Storage Ring Complex
In the case of the EPU on ALS beamline 4.0.2, the polarization can be changed from
left to right circular polarization in a few seconds, and the peak energy can be varied
as quickly as the monochromator scans [54,55].
A final note—why are the frames for these IDs so huge? It turns out that when the
gaps are closed down, the magnetic forces between the jaws are enormous—several
thousand Newtons per meter of length. For a 3 meter insertion device, this translates
to over 10,000 Newtons or over a ton of force. No wonder the overall assemblies can
weigh ~9000 kg!
2.6 Suggested Exercises
1. What is the bend radius for a dipole magnet with a field of 2 Tesla for an electron
beam with an energy of 2 GeV?
2. What is the approximate focal length of a quadrupole doublet where the field
gradient for each quadrupole is 10 Tesla/m, the length of the magnets is 0.3 m, the
separation between the magnets is 3 m, and the beam energy is 2 GeV?
3. Using approximate values from Fig. 2.10, calculate the minimum and maximum
horizontal beam sizes for the Sirius storage ring. Assume the horizontal emittance
is 0.28 nm rad.
4. The MAX-IV ring has a circumference of 528 m and runs with a microwave
frequency of 99.931 MHz. Calculate the harmonic number h.
5. Consider a Nd 2 Fe 14 B magnet PPM insertion device with rectangular blocks, an
undulator period of 68.3 mm, and a minimum gap of 23.82 mm. If we assume that
the magnet remanent field was 1.26 T, what would the maximum field be at the
device center?
6. Compare a SmCo 5 hybrid magnet undulator with a remanent field B r ¼ 0.9 T with
a Nd 2 Fe 14 B hybrid with a remanent field B r ¼ 1.3 T. In both cases, assume high
permeability (vanadium-permendur) alloy pole pieces. Calculate the fields at a
1.2 cm gap if the undulator magnetic period is 7.00 cm. (You will have to research
the proper formula for the latter device.)
7. One sometimes reads that high-energy electrons are at the front of the bunch,
because they have a higher velocity. Calculate the difference in transit times for
electrons of energy 2.9 and 3.1 GeV, if they were to travel along a perfect circle
with a circumference of 500 m.
2.7 Reference Books and Review Articles
1. Particle Accelerator Physics—Basic Principles and Linear Beam Dynamics;
H. Wiedemann, Springer-Verlag: Heidelberg, fourth Edition, 2015, ISBN
978-3-662-02903-9—in-depth treatment of accelerator and storage rings.
36
2 The Storage Ring Complex