For the purpose of carrying out his duties, the Sergeant at Arms and Doorkeeper of the Senate is authorized to incur official travel expenses during each fiscal year not to exceed the sums made available for such purpose under appropriations Acts. With the approval of the Sergeant at Arms and Doorkeeper of the Senate and in accordance with such regulations as may be promulgated by the Senate Committee on Rules and Administration, the Secretary of the Senate is authorized to advance to the Sergeant at Arms or to any designated employee under the jurisdiction of the Sergeant at Arms and Doorkeeper, such sums as may be necessary to defray official travel expenses incurred in carrying out the duties of the Sergeant at Arms and Doorkeeper. The receipt of any such sum so advanced to the Sergeant at Arms and Doorkeeper or to any designated employee shall be taken and passed by the accounting officers of the Government as a full and sufficient voucher; but it shall be the duty of the traveler, as soon as practicable, to furnish to the Secretary of the Senate a detailed voucher of the expenses incurred for the travel with respect to which the sum was so advanced, and make settlement with respect to such sum. Payments under this section shall be made from funds included in the appropriations account, within the contingent fund of the Senate, for the Sergeant at Arms and Doorkeeper of the Senate, upon vouchers approved by the Sergeant at Arms and Doorkeeper.