1. f Project-X Related Issues in Recycler A.Burov, C.Gattuso, V.Lebedev, A.Leveling, A.Valishev, L.Vorobiev Fermilab AAC Review 8/8/2007

2. f 8/8/07 – A.Valishev 2 Outline  Overview of machine parameters  Phase space painting at injection  Coherent stability  Particle losses and Radiation issues  Beam loss management and Radiation protection

3. f 8/8/07 – A.Valishev 3 Recycler Parameters Number of particles 1.7×10 14 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 Q h /Q v 20.45/20.46 Betatron tune chromaticity -20 Synchrotron tune (maximum) 0.0067 Transverse acceptance 40  mm·mrad Momentum acceptance ±3.2×10 -3

4. f 8/8/07 – A.Valishev 4 Phase 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

5. f 8/8/07 – A.Valishev 5 Longitudinal 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

6. f 8/8/07 – A.Valishev 6 Transverse 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

7. f 8/8/07 – A.Valishev 7 Coherent 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

8. f 8/8/07 – A.Valishev 8 Beam 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 I accept =40  mm·mrad, I beam =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 3x10 7 protons/s (0.03 W) [1] V.Lebedev, S.Nagaitsev, FERMILAB-Conf-02/099-T

9. f 8/8/07 – A.Valishev 9 Radiation Resistance of Permanent Magnets  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

10. f 8/8/07 – A.Valishev 10 Beam Loss Management and Radiation Protection  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

11. f 8/8/07 – A.Valishev 11 Beam Loss Management Goals Beam Energy (GeV) Beam Power Protons / second Region Type Peak Acceptable Uncontrolled Losses (W/m) Peak Acceptable Uncontrolled Losses (protons/ m/sec) Estimated Percent of Controlled Beam Power Loss Design Controlled Losses (KW) 8 153 KW 1.2e14 Beam pipe 0.251.95e8NA 8 153 KW 1.2e14Magnet3 to 10 2.34e9 to 7.81e9 1%1.5 120 2.3 MW 1.2e14 Beam Pipe 0.251.3e7NA 120 2.3 MW 1.2e14Magnet3 to 10 1.56e8 to 5.21e8 0.1%2.3 KW

12. f 8/8/07 – A.Valishev 12 Collimation 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

13. f 8/8/07 – A.Valishev 13 Residual Radiation and Component Activation  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

14. f 8/8/07 – A.Valishev 14 Electronic 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.

15. f 8/8/07 – A.Valishev 15 Radiation Shielding, Water and Air Activation  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.

16. f 8/8/07 – A.Valishev 16 Summary  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…

17. f 8/8/07 – A.Valishev 17 Summary 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