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

Septum Magnet parameters Beamline Optics: J.Doornbos ( ) Engineering/Design & construction of Septum magnet  Possibly at KEK Septum magnet parameters (from J.Doornbos optics studies) : Length = 1.5 m;B-field = kG; Bend = 145 mr ( 8.31º );Bend radius = 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 stripper foil  Halo of order 10 –5  ~ 1 nA ( for 120  A main beam ) BL1A UCN (T1 / M11-septum)

Dipole Magnet parameters Beamline Optics: J.Doornbos ( ) Engineering/Design & construction of Dipole magnet  Possibly at KEK BL1A UCN (T1 / M11-septum) 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 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.

Dipole Magnet Fringe Field Order-of-magnitude/“Sanity-check” estimate of fringe field constraints: For ~500 MeV protons  (Rigidity) –1 is ~ rad/11.7 kG-m  275 mr / Tm 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):  DAC(SM7) = 227  dx ~ 5 mm (at T2, dz ~ 8.6 m)  d  x ~ 0.58 mr  DAC(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)  BdL ~ Tm = 20 Gm 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)  BdL ~ Tm = 90 Gm 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.