1. PROPOSAL 2006 - G.I.A.F. (HYBRID GUN AT HIGH FREQUENCY) INFN-LNF – UNIVERSITY OF ROME “LA SAPIENZA”- UCLA D. Alesini (T), M. Ferrario (R), A. Gallo (T), F. Marcellini (T), V. Fusco (art. 23), B. Spataro (T) (Resp. Naz.) LNF Full Time Equivalent 1.5 (1.3 tecnologist – 0.2 researcher) L. Ficcadenti (D), M. Esposito (AU), M. Migliorati (R), A. Mostacci (consultant), L. Palumbo (PO) University of Rome Full Time Equivalent 1.2 (0.6 tecnologist – 0.6 researcher) J. Rosenzweig(PO) UCLA Dept. of Physics and Astronomy Full Time Equivalent 1.0 (R) TOTAL FTE 3.7

2. HYBRID GUN ELECTROMAGNETIC DESIGN AND RF MEASUREMENTS 2)DESIGNED STRUCTURES: a)Integrated accelerating structure; b)Integrated velocity bunching (acceleration+longitudinal bunch compression); 3) POSSIBLE MEASUREMENTS ON PROTOTYPES 1) THE HYBRID STRUCTURE: ADVANTAGES

3. SW 1.6 Cell Gun Input Cell Emittance-Compensating Solenoids Cathode TW structure Input Port 1) THE HYBRID STRUCTURE

4. 1)Eliminate transient reflection associated with SW structures (especially needed for X-band); 2)Compactness: -simplicity (RF distribution system, etc.) -energy efficiency from TW section 3)Promising good beam dynamics in term of beam emittance and reachable bunch length (velocity bunching) 1) THE HYBRID STRUCTURE: ADVANTAGES

5. 2)DESIGNED STRUCTURES: GENERAL CONSIDERATIONS The steps to design the structure are the following: a) “Separate” tuning of the SW and TW sections in order to achieve a uniform field flatness of the E field in the SW gun and a zero reflection coefficient at the waveguide input port of the TW section at the working frequency of the whole system; b) Final tuning of the whole structure to put the SW section perfectly on resonance with a uniform field flatness of the E field in the first two cells;

6. 1) the phase of the E field between the SW gun and the TW section does not depend on the geometry of the input coupler cell, iris dimensions,… and is about 90 deg. This results has been found by 3D electromagnetic simulations and has been justified with an equivalent circuit model; 2) the coupling iris aperture between the input coupler cell and the SW structure allows adjusting the ratio beween the amplitude of the fields in the SW cells and in the TW section: in particular if we increase the radius we increase this ratio; RESULTS (S-Band Case) E.M. field characteristics @ gun resonance Input coupler cell  90 deg E z (z,t)=E 0 (z)cos(ph(z)+  t)

7.  Mode of the gun 4) Since the phase between the SW structure and the TW one is fixed, the synchronism between the accelerating field and the bunch passage can be adjusted by properly chosing the lenght of the input coupler cells. It is therefore possible to design two different structure: -the first one obtainded choosing Dc=2/3 in which the beam is accelerated in both structures SW gun and and TW section; -the second one obtained by choosing Dc=5/12 in which the bunch is accelerated in the SW section and longitudinally compressed (velocity bunching technique) in the TW one; Dc 3) for reasonable values of the coupling iris (that gives a ratio between the amplitude of the fields up to 5) the perturbation on the matching of the input coupler waveguide is completely negligible.

8. 0.5deg/kHz Integrated velocity bunching (1/2) Amplitude of the E field along the structure (E 0 (z)) Phase (ph(z)) of the electric field along the structure: the sensitivity of the phase with respect to the resonant frequency of the SW structure requires very good stabilization of the temperature or an RF feedback E z (z,t)=E 0 (z)cos(ph(z)+  t)

9. E acc z z Input coupler Output coupler Traveling wave structure z bunch Integrated velocity bunching (2/2) E acc

10. Integrated velocity bunching dimensions acac bcbc dcdc t a b d awaw b w /2 w/2 h bfbf bhbh dfdf dhdh tgtg tctc agag acac 9 [mm] tctc 19.05 bcbc 40.93 dcdc 43.74 t8 a16 b42.89 d34.99 h2 awaw 30.21 bwbw 72.14 bfbf 41.7 dfdf 52.48 tgtg 19.05 agag 12.5 bhbh 41.67 dhdh 31.49 w35.2

11. Integrated accelerating structure dimensions acac bcbc dcdc t a b d awaw b w /2 w/2 h bfbf bhbh dfdf dhdh tgtg tctc agag acac 9 [mm] tctc 19.05 bcbc 40.53 dcdc 69.98 t8 a16 b42.89 d34.99 h2 awaw 36.09 bwbw 72.14 bfbf 41.7 dfdf 52.48 tgtg 19.05 agag 12.5 bhbh 41.67 dhdh 31.49 w33.3

12. 3) RF MEASUREMENTS Steele method (C.W. Steele, IEEE trans. on micr th. and tech., 1965) is applicable to SW and to TW structures separately; Difference between the reflection at the input port with and without the perturbing object at z longitudinal position Pertubing objects Hybrid gun NA z

13. PARMELA simulations Input Beam Parameters: Q=1 nC L TW =3 m T 0 =10 psec R b =1.57 mm  0 =40 deg

14. Magnetic field

15. Energy gain and Momentum spread evolution

16. Bunch length and Transverse beam size evolution

17. Emittance evolution

18. SPARC (S Band)HYBRID (S Band) ModeNormalRF Compr. NormalRF Compr. Total Length [m]12 33 Energy [MeV]2201805022 Energy Spread [%]0.11.00.31.5 Peak Current [A]100800100400 Rms norm. emittance [  m] <2 <4

19. Work planning 2007 1Design of the hybrid structure at 3 GHz (velocity bunching); 2Construction of a prototype at 3 GHz with no cooling and brazing for the measurements at room temperature; beam dynamic simulation ; 3Some tests for brazing on some cells. 2008 1Design of the hybrid structure at 11 GHz (velocity bunching); 2Construction of a prototype at 11 GHz with no cooling and brazing for the measurements at room temperature; beam dynamic simulation ; 3Tests for brazing on some cells. 2009 1Design of a hybrid structure at 11 GHz included the cooling system; 2Construction of a brazed hybrid structure and measurements at room temperature; 3High power tests for structures at 3 GHz and 11 GHz

20. Estimates costs 2007 Costs ( 3 GHz) 1 hybrid structure61.0 KEuro 2 waveguide tapers10.0 KEuro Brazing tests5.0 KEuro Consumable3.0 KEuro Durable equipment8.0 KEuro 2008 Costs (11 GHz) 1 hybrid structure 37.0 KEuro 2 waveguide tapers 8.0 KEuro Brazing tests5.0 KEuro Consumable3.0 KEuro Durable equipment8.0 KEuro 2009 Costs (11 GHz) 1 hybrid structure 90.0 KEuro 2 waveguide tapers 10.0 KEuro Brazing tests5.0 KEuro Consumable13.0 KEuro Durable equipment8.0 KEuro Domestic travel/year2.0 KEuro Abroad travel/year5.0 KEuro

21. SUMMARY COSTS Domestic travel (KEuro) Abroad travel (KEuro) Consumable (KEuro) Durable equipment (KEuro) Equipment constructions (KEuro) 2007 2.010.08.0 71.0 2008 2.010.08.0 40.0 2009 2.010.013.0 8.0 90.0 Total 6.030.029.024.0201.0 Consumable : attenuator, connectors, cables, vacuum components (flanges, gaskets, valves), ceramic transitions, brazing alloys etc. Durable equipments : guide transitions, loads, directional coupler, power supply Equipment constructions : hybrid structure included 2 waveguide tapers