BL1U at TRIUMF UCN Beamline Septum & Dipole Magnets (April 12, 2010)

1. BL1U at TRIUMF UCN Beamline Septum & Dipole Magnets (April 12, 2010)

2. UCN BL1A (T1 / M11-septum) Septum Magnet parameters Beamline Optics: J.Doornbos ( https://documents.triumf.ca/docushare/dsweb/ServicesLib/Document-27248/Document-27248 ) Engineering/Design & construction of Septum magnet  Possibly at KEK Septum magnet parameters (from J.Doornbos optics studies) : Length = 1.5 m; B-field = 3.515 kG; Bend = 145 mr ( 8.31º ); Bend radius = 10.34 m; Distance from UCN beam to BL1A: 6.0 cm at septum entrance 19.0 cm at exit of septum Beam sizes (full size at 2 contour): 11 mm wide x 13 mm high [septum entrance] 9 mm wide x 15 mm high [septum exit] Vertical aperture: 10 cm (full gap) Horizontal aperture: Depends on details of construction at entrance; assumed to be 15 cm full width at exit. Sagitta: 2.7 cm (The sagitta is the maximum distance between the curved path of the beam and the straight line drawn between the points at the entrance and exit). Radiation Environment: From beam halo  Require more/detailed beam studies in BL1A to adequately quantify Simulation studies ( Y.-N.Rao )  Large-angle scattering @ stripper foil  Halo of order 10 –5  ~ 1 nA ( for 120 mA main beam )

3. UCN BL1A (T1 / M11-septum) Dipole Magnet parameters Beamline Optics: J.Doornbos ( https://documents.triumf.ca/docushare/dsweb/ServicesLib/Document-27248/Document-27248 ) Engineering/Design & construction of Dipole magnet  Possibly at KEK Dipole magnet parameters (from J.Doornbos optics studies) : Length = 1.2 m (central trajectory); B-field = 9.78 kG; Bend = 18.5º; The“Straight Thru” length is 1.195 m; Distance from UCN beam to BL1A: ~ 60.0 cm; (fringe field at BL1A?) Beam sizes (full size at 2 contour): ~ 7 mm wide x 21 mm high Vertical aperture: 10 cm (full gap) Horizontal aperture: 15 cm (full width) Sagitta: 4.8 cm (The sagitta is the maximum distance between the curved path of the beam and the straight line drawn between the points at the entrance and exit). Fringe Field Constraints: At BL1A ( ~ 60 cm from UCN beam ), dipole fringe fields could have effect on main beam. More detailed studies required to determine fringe field constraints.

4. Dipole Magnet Fringe Field Order-of-magnitude/“Sanity-check” estimate of fringe field constraints: For ~500 MeV protons  (Rigidity)–1 is ~ 0.323 rad/11.7 kG-m  275 mr / T•m BL1A feedback loops (3) keep beam centered on targets at T1, T2, TNF  Target Protect monitors (U,D,L,R) coupled to steering magnets (V,H) Steering Power of feedback magnets (data from recent T2 scan using SM6 & SM7): DDAC(SM7) = 227  dx ~ 5 mm (at T2, dz ~ 8.6 m)  dx ~ 0.58 mr DDAC(SM6) = 184  dy ~ 5 mm (at T2, dz ~ 9.0 m)  dy ~ 0.56 mr To deflect beam by ~ 0.56 mr (from dipole fringe field)  B•dL~ 0.002 T•m = 20 G•m If we assume dL(UCN-dipole fringe field region) dL(main field region)  1.2 m  then feedback loops could correct for effects from dipole fringe field of ~ 17 G Max DAC settings for SM7 & SM6 is 1023  dx(max) ~ 2.5 mr , dy(max) ~ 3.0 mr (Note: There are 2 Quads between SM6/7 & T2, so this scaling is questionable) To deflect beam by ~ 2.5 mr (from dipole fringe field)  B•dL~ 0.009 T•m = 90 G•m If dL(dipole fringe field)  1.2 m  then feedback loops may be able to correct for effects coming from dipole fringe fields of  75 G Caveat: As there are a number of Quad’s between the UCN-dipole fringe field region, the various feedback steerers, and the various Target Protect monitors, more in-depth studies (with the full BL1A optics & simulations of the dipole fringe fields) are required to adequately determine the fringe field constraints.