F Project-X Related Issues in Recycler A.Burov, C.Gattuso, V.Lebedev, A.Leveling, A.Valishev,...

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Project-X Related Issues in Project-X Related Issues in RecyclerRecycler

A.Burov, C.Gattuso, V.Lebedev, A.Leveling, A.Valishev, L.Vorobiev

Fermilab AAC Review8/8/2007

8/8/07 – A.Valishev 2

f OutlineOutline

Overview of machine parameters Phase space painting at injection Coherent stability Particle losses and Radiation issues Beam loss management and Radiation

protection


f Recycler ParametersRecycler Parameters

Number of particles 1.7×1014

Longitudinal emittance 0.6 eV s

Momentum spread (100%) ±2.5×10-3

Transverse emittance (100%) h=v

25 mm·mrad

Harmonic number 588

Number of bunches 548

Main RF Frequency 52.811 MHz

Main RF Voltage 750 kV

Second Harmonic RF Voltage 375 kV

Betatron tunes Qh/Qv 20.45/20.46

Betatron tune chromaticity -20

Synchrotron tune (maximum) 0.0067

Transverse acceptance 40 mm·mrad

Momentum acceptance ±3.2×10-3


f Phase Space PaintingPhase Space Painting

Motivation Gaussian beam G =3 Single RF harmonic at 53 MHz B =5

Q=-0.3

Uniform beam G =1 Longitudinal painting B =2

Q=-0.04

BGN

N

320

14

2

r-Q

mrad mm25

107.1


f Longitudinal PaintingLongitudinal Painting

Bunch emittance from linac 2.5x10-6 eV·s Recycler bunch emittance 0.6 eV·s

1300MHz/4 bunches from linac

6.15 bunches per 52.8MHz bucket

1ms pulse = 89 turns Chop 2 bunches – 356

bunches/bucket/1ms pulse Sweep energy ±9MeV during

the 1ms pulse

B=2.2


f Transverse PaintingTransverse Painting

Linac bunch transverse emittance 2.5 mm·mrad (95%)

Recycler bunch emittance 25 mm·mrad (K-V distribution)

Horizontal offset center maximum Vertical angle maximum center

D.Johnson et al., TUPAS020, PAC2007


f Coherent StabilityCoherent Stability

Resistive wall Well understood Unstable mode at fractional betatron tune ~50kHz Growth time 10 turn

Electron cloud Only rough estimates were made Unstable modes ~10-50 MHz Growth time 10 turns (assuming 20% charge

compensation) Both can be Landau damped

Chromatic tune spread must be > tune shift 0.04 for energy spread of 0.25% obtained at chromaticity -

16 Broadband damper should be foreseen Large synchrotron tune spread (100%) damps

longitudinal and transverse instability An extensive simulation of lifetime/losses has to be

provisioned


f Beam Halo and LossesBeam Halo and Losses

Provided that there are no istabilities, particles will be lost due to two effects

Single Coulomb scattering on the foil at injection Based on the calculation in [1] we derive for K-V distribution

For Iaccept=40 mm·mrad , Ibeam=25 mm·mrad and 5 passages through the foil dN/N=4x10-4.

This corresponds to 130W power loss which should be controlled by the use of collimation system

Scattering on residual gas Very weak. The achieved lifetime in the Recycler is ~1000

hours at 10-10 torr or the total loss rate of 3x107 protons/s (0.03 W)

[1] V.Lebedev, S.Nagaitsev, FERMILAB-Conf-02/099-T

beamacceptfn

p

IInZZ

r

N

dN

1)1(

22

2


f Radiation Resistance of Permanent Radiation Resistance of Permanent MagnetsMagnets

Permanent magnets built using strontium ferrite bricks have been tested for stability against demagnetization [1]

During the tests, no loss of magnetization was observed for bricks exposed to a proton beam, and a magnet exposed to several Gigarads of Co60 gamma radiation suffered no measurable demagnetization.

A magnet exposed to 0.8 Mrad/hour for 268 hours showed the magnetic field change of about 0.5 Gauss out of 1465 Gauss, or ~2 X10-4 which is within of allowed variations. [2]

[1] e.g. J.T.Volk, FNAL report, http://home.fnal.gov/~volk/rad_damage/summary%20of%20radiation%20damage%20studies%20on%20rare%20earth%20permanent%20mangets.pdf

[2] MI Note 150


f Beam Loss Management and Radiation Beam Loss Management and Radiation ProtectionProtection

Radiation protection can be realized for this project through the straight-forward process of beam loss management

Two basic requirements for radiation protection must be observed Regulatory requirements related to health and safety

of workers, the public, and the environment (FRCM) Practical machine control requirements necessary to

protect machines from short term and long term damage due to beam loss


f Beam Loss Management Goals Beam Loss Management Goals

BeamEnergy (GeV)

Beam

Power

Protons/

second

Region Type

Peak Acceptable Uncontrolle

d Losses (W/m)

Peak Acceptable Uncontrolle

d Losses (protons/m/sec)

Estimated Percent of Controlle

d Beam Power Loss

Design Controlle

d Losses (KW)

8153 KW

1.2e14Beam pipe

0.25 1.95e8 NA NA

8153 KW

1.2e14Magne

t3 to 10

2.34e9 to 7.81e9

1% 1.5

1202.3 MW

1.2e14Beam Pipe

0.25 1.3e7 NA NA

1202.3 MW

1.2e14Magne

t3 to 10

1.56e8 to 5.21e8

0.1% 2.3 KW


f Collimation SystemsCollimation Systems

Collimation systems are planned For the 8 GeV transfer line just downstream of the 8

GeV linac For the Main Injector accelerator An H- stripping foil/collimation system will also be

included at Recycler Ring injection system


f Residual Radiation and Component Residual Radiation and Component ActivationActivation

Residual Radiation levels in Tunnels Peak acceptable uncontrolled beam power losses

listed in Goals result in a radiation dose rate of 100 mrem/hr at a distance of 30 cm from the component (beam tube or magnet) surface

The average dose rate at 30 cm from all components should be a factor of 5 lower or 20 mrem/hr at 30 cm

Accelerator Component Activation Based upon Fermilab operating experience

observation of acceptable beam losses in Goals will not lead to radiation damage concerns for accelerator magnet and cable systems


f Electronic BermElectronic Berm

It is impractical to use shielding alone to mitigate the consequences of prolonged high power beam loss for various radiological problems

It is important to promptly turn off high power accelerators in the event high power beam loss occurs

Electronic berm is a safety system that can be used to meet the regulatory requirements for this project. By comparing beam intensity signals the electronic berm can detect a high power beam loss and inhibit further operation of the machine in one Main Injector machine cycle.


f Radiation Shielding, Water and Air Radiation Shielding, Water and Air ActivationActivation

Radiation Shielding The existing Recycler Ring/Main Injector beam

enclosure has a minimum of shielding thickness of 24.5 feet

To limit the maximum accident radiation dose rate to 1 mrem/hr and the normal condition dose rate to 0.05 mrem/hr, the beam power loss at a point for these two conditions is beyond the limit set by control of acceptable losses inside the beam enclosure

Surface and Ground Water and Air Activation Scaling from existing conditions and assuming the use

of additional controls to limit uncontrolled losses in the Recycler and Main Injector machines, the surface water activation, ground water activation and air activation should remain well within acceptable limits.


f SummarySummary

No principal limitations from the point of view of accelerator physics have been found for the high intensity operation of the Recycler.

We foresee no significant modifications to the machine magnets or vacuum system.

Major upgrade concerns the RF system where the second harmonic system is added.

Phase space painting is feasible to mitigate space charge effects

Coherent instabilities can be suppressed by betatron tune chromaticity and broad-band damper

continued…


f Summary continuedSummary continued

Under normal conditions total losses should not exceed 300 W (controlled by injection collimation system)

Recycler permanent magnets are capable of withstanding high radiation doses

Radiation protection for the project can be realized using Beam loss management Collimation systems and electronic berm are

envisaged

Future efforts could include More detailed lattice and RF design Dynamics simulations with space charge E-P instability studies

F Project-X Related Issues in Recycler A.Burov, C.Gattuso, V.Lebedev, A.Leveling, A.Valishev,...

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